What’s Up with Measles and the MMR Vaccine? – PediaCast 431
- We have a measles problem in the United States with record numbers of infections and large outbreaks in five states. So, what’s up with measles and the MMR vaccine? We explore the disease, including cause, symptoms, complications, treatment and prevention. Then we’ll cover MMR: How does it work, what’s in it and how safe are the ingredients? It’s a measles extravaganza you won’t want to miss!
Announcer 1: This is PediaCast.
Announcer 2: Welcome to PediaCast, a pediatric podcast for parents. And now, direct from the campus of Nationwide Children's, here is your host, Dr. Mike.
Dr. Mike Patrick: Hello, everyone. And welcome once again to PediaCast. It is a pediatric podcast for moms and dads. This is Dr. Mike coming to you from the campus of Nationwide Children's Hospital. We're in Columbus, Ohio.
It is Episode 431 for May 1st, 2019. We're calling this one "What's Up with Measles and the MMR Vaccine?" I want to welcome all of you to the program.
So unless you've been living under a rock, you have heard the news that we have a problem with measles in the United States. And this is a statement that I could not imagine saying when I started PediaCast back in 2006, which was just six years after the US Centers for Disease Control and Prevention declared measles eradicated from the United States. So I never saw case of measles in medical school, in residency, in private practice. Just didn't see it.
And what the CDC though did not count on is the subsequent decline in vaccination rates that we have seen in recent years resulting from vaccine fears and vaccine hesitancy. And that's resulted in a vulnerable population. Now combine that with easy travel from areas of the world where measles has not been eradicated and you have the perfect storm for an outbreak of disease and that's exactly what we've seen.
Numbers of measles cases in the United States had hit a post-eradication high in 2014, and that was the year we had 667 reported cases. Many of them associated with an outbreak that saw Disneyland at the epicenter and resulted in stricter vaccination laws in California. Thanks to state senator, Dr. Richard Pan.
Now here in 2019, we have surpassed that number. We're up over 700 cases as we chat here on May 1st, 2019. And we have current outbreaks in New York, City, Rockland County, New York, Washington State, New Jersey, Butte County, California, and Michigan. And it could be heading your way next or my way, any which way really.
All it takes are unvaccinated folks, 90% of whom will catch measles when they're exposed to it and a visitor with measles which is contagious for about five days before the rash begins. You can see, you have someone come along with measles, they don't even know they have it. They just have runny nose, congestion, maybe some eye redness, and discharge or cough, no rash, fever. And they exposed an unprotected population. You can see how an outbreak could happen pretty easily.
Now, so what's the big deal? Well, the issue is that measles is not a mild disease. 5 to 10% of those infected developed a life threatening pneumonia. And that has played out if you look at the number of hospitalizations or severe cases of pneumonia associated with this current measles outbreak. It is about 5 to 10%.
So we've had 60 to 70 hospitalizations, again, primarily for pneumonia with measles. We can expect about 1 in 1,000 to experience encephalitis which is brain swelling. And one to two cases out of every thousand of measles results in death.
Measles is a pretty serious business. And as the disease counts claims closer and perhaps eventually over a thousand cases, we can expect to hear about kids who have a very unfortunate outcomes from this. Not only death but also permanent brain injury, deafness. We're starting to see reports on social media of adults who are deaf and that is because they had measles at some point in their childhood.
Just had one that had what we call subacute sclerosing panencephalitis. We're going to talk more about exactly what that is. But I saw report on social media someone who had that particular problem. It's very serious and again, we'll talk more about what it is.
But this person that we heard a parent talked about had a measles when they were less than a year old. They hadn't had their MMR vaccine yet. They were not protected. And now, it's several years later that they developed these complications from the measles.
It is a serious business and we want to take it seriously. And with all of these in the news, the outbreaks, vaccine hesitancy, state legislators scrambling to either tighten or loosen vaccine laws depending on where you live, I thought it would be a good idea to devote an entire episode of PediaCast to measles and the MMR vaccine.
And here is my pledge to you. I'm not going to be overly dramatic about this. I want to share the facts about measles and the MMR as we know them and then I'll let you decide.
We're going to cover measles, the disease, how it's contagious, symptoms, complications, treatment, prevention. My goal is really for you to come away from this episode feeling a little bit like a measles expert.
And then, we'll consider prevention. And in particular with prevention, we're going to land on the MMR vaccine including the history of its development, which is pretty interesting, how it works, the vaccines effectiveness, controversies surrounding its use, side effects, complications, risks.
And I'm not going to sugarcoat it. Okay, there are some risks that we know about the MMR vaccine. I want to be transparent about that and paint a clear picture of what those risks are.
Now in the end, I think the data points towards vaccinating your children with the MMR vaccine. And I say that not because I'm a pediatrician. Some would say, "Well, you're supposed to say that, right?" No, I say it because in my opinion, that's what the evidence suggests.
And I say that as a scientist and someone who understands how to read the literature, what the different components of things mean including the Vaccine Adverse Event Reporting System, which we'll talk about a little bit later on, and also the vaccine compensation funds and vaccine court. Some people would say, "Well, this is evidence that this is a dangerous thing."
I want to really talk about all of these things in an objective way. Just what are the facts, what are they, what does it all mean when we put these altogether and look at all of the risks and all of the benefits on both sides of the equation. Now once I have considered all of these things, I don't think it will come as much of a surprise to you, folks, that I would give my kids the MMR vaccine.
I did it back 22 and 24 years ago and I would do it again in a heartbeat. That's where I land in terms of looking at risks and benefits considering my own risk tolerance. That said, your risk tolerance may be different.
And I'm not approaching the podcast today with an agenda to change anyone's mind. I hope everyone does change their mind, but this is not an argumentative case. I just really want to present the facts for you, talk about what we know, and just see where it takes us as we consider measles and the MMR vaccine. I hope you'll keep listening and join me on the trip.
Before we get started, a couple of things, you can catch PediaCast on Facebook, Twitter, Instagram. We try to provide more content than what you'll get on the program here. We share news parents can use, news articles, just blog posts from other pediatricians. Just things I think parents will be interested in, those things primarily on Facebook and Twitter. Just search for PediaCast. You can find them pretty easily.
On Instagram, we try to have some more pictures into the studio and just in my life in general, our family, what's going on. We are people, in addition. All medical professionals are people too, so we got things going on our lives. It's kind of fun to share those on Instagram. I love to see what's happening with you as well. If you follow PediaCast on Instagram, expect us to try to follow you back. Just, you know, I want to try to build community in that space.
Let's go ahead and take a quick break and then I will be back. We'll take more about measles and the MMR vaccine. That's coming up right after this.
Dr. Mike Patrick: We are back and we're going to talk about measles. Rubeola is the disease name that the measles virus causes. If you want to be technical about what we call this illness, it's rubeola or measles. Just so if you hear that name, rubeola, measles, means the same thing.
It's caused by the measles morbillivirus and that is in the family Paramyxovirus. It's a single-stranded RNA, for those of you keeping score. And we have some medical folks in the audience. I even know of a microbiologist who sometimes listens.
So it's a single-stranded RNA virus. Like all viruses, it invades cells in the body. It sort of takes over the factory systems in cells. Cells make protein and it uses DNA to do that. Although DNA is a code and so it tells the cell how to put amino acids together to make a protein.
And in this case, what the virus does is it takes over those mechanisms and instead of making a protein, it makes more of itself. And so the cell makes more and more measles virus until there's so many in there, it can't contain them anymore. The cell bursts open and all those viruses spill out. It kills the cells and after it hijacks the cells to be used as it little factory to make more of itself. That's how viruses work.
And the difference in terms of what sort of symptoms you get with a particular virus, in terms of which body systems, whether it's respiratory, whether it's something that's the GI track, you get vomiting and diarrhea or you get like the flu, mostly runny nose, congestion cough, depends on which cells get invaded by the virus.
So in terms of the measles virus, it primarily affects the upper respiratory system, so you do like the flu, you get runny nose, congestion and cough. And it also very frequently, in fact, almost always infects the conjunctiva, which is the clear outer layer lining of the eyes. So you basically get like a pinkeye or conjunctivitis with the runny nose congestion, very bad cough, and fever.
It can travel elsewhere. And we'll get into the specific symptoms and how often they occur but it can sometimes cause some vomiting and diarrhea. The rash is actually a by-product of the immune system at work. So the rash that we see with measles is not that the viruses infecting the skin, it's a consequence of the immune system and what it's doing to try to rid the body of this virus that is hijacking cells and turning them into little self-reproducing factories.
In terms of a being contagious, it's in the upper respiratory tract. It actually is in respiratory droplets. So you know when you cough or you sneeze into your hand, it feels wet. What makes it feel wet are what we would call respiratory droplets.
And so the measles virus, because it's infecting the upper respiratory tract, it is contained within these respiratory droplets. And the virus is pretty hardy. It can live up to two hours in these respiratory droplets.
It can be suspended in the air. It can be on surfaces, on doorknobs, counters, anything that someone coughs or sneezes unto or into their hand and they touch. It can be on those surfaces and it could just linger in the air. And they can do that for about two hours.
So someone with measles can cough or sneeze into the air, leave the room or leave the area, and it can still be there ready to infect you up to two hours later. That's pretty impressive.
It is also highly contagious. If a person does not have immunity against measles and they come into contact with it, we can expect about a 90% transmission rate. So pretty highly contagious.
And then here's the kicker, it's contagious for about five days before the rash appears and for about four days afterward. So it has a pretty characteristic rash which we're going to talk about. And that kind of gives a lot of people the first clue, "Hey, this could be the measles because what the rash looks like."
But for five days before that, while the person just has fever, runny rose, congestion, cough, conjunctivitis, which is very common with other viruses as well, they are contagious. And so that's one of the reasons it spreads so easily and very difficult to contain.
What about incubation period? A little bit longer than the flu and your common cold viruses, one to three weeks in terms of when you start to see disease with an average of about two weeks. This also makes it sort of hard to contain because you may not see where people are getting it from for a couple of weeks afterwards. So it takes a little bit of time not to be contagious before you see evidence of it's contagious right away.
But before you see evidence of disease can be up to two weeks later. And then, that's when they're going to be contagious with it. So a long incubation period compared to some other viruses.
What do you see? Well, we mentioned at the beginning, actually fever is one of the first things. And just what we would say it malaise. In our family, we call it, "You feel viral." You just don't feel well. You may feel a little bit achy. You're tired. You don't really feel like eating a lot. You just want to lie on the couch and be left alone.
And that's sort of the beginning for a couple of days. And then, if the fever hadn't started, it's definitely going to start now. You'd get what we had mentioned, the runny nose, congestion, cough.
We call it coryza, just lots of mucus. And so you're blowing your nose a lot, you're coughing a lot, pinkeye, conjunctivitis.
And then, about two to three days in, you start to get a little spot, a little rash basically inside of the mouth in the oral mucosa. And this had been described as a grain of sand on an erythematous base. So erythematous means it's red. So it's kind of red base and a little white in the middle of it like a grain of sand.
And these are called Koplik's spots. And I suspect that they're named after probably Dr. Koplik, who figured this out that they are associated with measles. That's my guess. I didn't look it up. Usually I look these things this historical things up but I didn't. And, of course, as soon as this is over, I want to look it up because I'm curious about it, who is Dr. Koplik?
But about around day two, you see this inside the mouth. Most commonly and what we would say the buccal mucosa, which is they're basically the insides of the cheeks. And we often sort of classic their opposite, the molars, on that buccal mucosa inside of the cheek, but then they spread throughout the whole mouth. The individual lesions can kind of coalesce into one big erythematous mess and then that gets better.
So that happens about two to three days in. And then, the rash begins about two to four days after the onset of the fever. Depending on whether you get the fever right away, it's more like four days. If you didn't get the fever for a day or two, then it's more like two days.
But this occurs after the spots in the mouth show up and it is what we call a fine maculopapular rash. Maculo just means that they are red spots, and papular means that there's some bumps. So some red, red spots and bumps.
And they begin on the face. And classically, they're going to begin behind the ears and then move to the rest of the face. And of course, not all kids follow the rule book and have this happen exactly. But sort of the classic picture is that it begins behind the ears and moves to the face and then it moves down and out. So from the face, it goes to the trunk, down at the arms, and down the legs, kind of in that progression.
That's classic. It's not what we'd considered pathognomonic, meaning there are other viruses that could give you that sort of a pattern of a rash as well. And sometimes measles isn't classic and you can get sort of an atypical measles. You can't count on the rash and the way it progresses to say it's measles.
The palms and the soles are rarely involved. The rash begins as discrete spots but then you get confluence of those spots. So what was sort of red spots and bumps kind of coalesce together to give you very large erythematous patches or red patches.
In the beginning, this rash blanches. Meaning, if you press on the skin, the redness goes away, the skin becomes more pale. And then, when you let go, the blood returns and then it becomes the normal rash color again. So it blanches in the beginning.
But then you can bleed into the skin and then that won't blanch. No matter how hard you push that bloods in the skin, it doesn't go away because you're not compressing blood vessels.
Then you'll get what we call petechia, which are little tiny bruises in the skin. Or you can even get hemorrhagic lesions where you really do bleed under the skin.
And then, this rash lasts for about a week and then it fades in the order in which it came. The skin kind of darkens. The rash darkens to a brownish color and then it desquamates, meaning that it gets like dry skin and sort of flakes off. And this is best seen in folks who don't have a lot of pigment in their skin. Caucasian, fair skin folks, and those with darker skin, African-Americans, etc., it can be more difficult to see these change from a red rash to sort of a dark brownish rash.
You can't always just go by the color of these rashes and paid especially when folks have more pigment in their skin because it can be difficult to differentiate and to describe it in sort of a classic sense.
In addition to the rash, you get some swollen lymph nodes, around the neck, into your cervical lymph nodes. You can get them elsewhere. You can get a pharyngitis, so it can infect the back of the throat, the tonsils. Again, that conjunctivitis or pinkeye is continuing and you still have the congestion, the cough, and the fever going on as you develop and during the course of this rash.
And then, the clinical symptoms do start to improve about halfway through the rash. The rash has been there for a few days. It's going to last about a week. The runny nose congestion, fever, pinkeye start to get better and then the rash fades.
And as long as there aren't any complications, that's it. Your immune system takes care of it. Again, the immune system is what causes the rash, not the virus itself.
The trouble is complications are common with the measles. And this is one of the reasons that people were motivated to create a vaccine because they saw these complications in their kids. They saw kids suffering. And we'll talk through this. And it was just a terrible thing that they wanted to create a vaccine in order to protect kids from the measles.
So the biggest complication we see is pneumonia in about 5 to 10% of cases. So about 5 to 10 out of every 100 cases of measles, you're going to get life-threatening pneumonia. The pneumonia can be caused from the virus itself. So the measles virus can invade down into the lungs and cause pneumonia.
It can also be from bacteria. Our mouth is full of bacteria. Your immune system's off fighting this virus. The bacteria can go a little bit unchecked. It go down to trachea, invade the lungs. Now, you have a bacterial pneumonia on top of the viral pneumonia.
And these pneumonias can be quite terrible. If it's a bacterial pneumonia only, then antibiotics may help if you get them started soon enough, unless you're colonized with resistant bacteria in your mouth and then that can be more difficult.
But the viral pneumonia of measles, if it's from the virus, antibiotics still help. You just have to support them with mechanical ventilation sometimes. Then, they can get sicker, become septic with bacteria in the bloodstream. And as it turns out, pneumonia and complications of pneumonia are the most common cause of death associated with the measles. And again, about 5 to 10% of cases will end up with pneumonia.
About 8% of the time, you do get some GI tract involvement, so you can get some vomiting and diarrhea. Hepatitis has been reported, so that's a liver infection with the virus or from your immune system. Can also cause inflammation of the liver, but that's rare. It is rare that you would get hepatitis and liver problems. Vomiting and diarrhea more common with measles.
Now, the one complication that people don't often talk about that's a significant one, and we're learning more about this, is that the virus can infect T-cells which are part of your immune system. And the T-cells, one of the things that they do is when your body is presented with a foreign substance, an antigen, is T-cells take the antigen to other cells and immune system and say, "Hey, this guy is not supposed to be here. Let's make antibodies against it. Let's activate some other cells of immune system to take care of this antigen."
And because the measles infects and causes this helper T-cells not to work quite as well, it ends up causing immunosuppression. And so, the immune system doesn't work as well after a measles infection. And that can actually last up to three years following infections. For about three years, after you get measles, you are at risk for more severe infections including ones you've been immunized against.
Things like prothesis, pneumococcus, diphtheria, things that we immunize people against in childhood that are serious significant diseases, you may not be as protected against those despite having been vaccinated once you had measles. And other illnesses that we do not vaccinate against, those can also be more serious, more severe because you have some immunosuppression because of what the measles does to the immune system itself.
You also may have heard about encephalitis. Encephalitis is an infection of the brain and the measles virus can cause this. That occurs actually in about one in a thousand cases. We've heard with these outbreaks not in the United States necessarily but in other countries here recently of folks suffering from encephalitis associated with the measles virus. And, again, about one in a thousand cases there.
With encephalitis, you get fever, headache, vomiting, stiff neck, seizures, and that can progress to coma and death. And again, antibiotics still help. It's not a bacteria, it's a virus. And so all you can do is support this people and hope that their immune system can take care of it.
Unfortunately, about a quarter of people who have encephalitis have long lasting effects of this that follow them the rest of their lives. They may have neurological deficits, motor problems, paralysis, sensory issues, cognitive brain function, issues down the roads of development problems. Deafness, we've heard some cases of that.
About a quarter of those who end up with encephalitis have that occurred. And about 15% of those with encephalitis rapidly progress to death. It kills them. And so encephalitis is another major player in terms of deaths from measles.
Another thing that you may have heard about is something called acute disseminated encephalomyelitis. And I know it's a mouthful, but this also occurs in about one in a thousand cases of measles. You don't have to have encephalitis for this to happen. This is something completely different.
And this is an autoimmune disease. So your immune system makes antibodies against measles. And I don't know that we know for sure, is it those particular antibodies or is it the immune systems stimulated in such a way an antibodies form against your nerves and your central nervous system? And so this can cause what we would call demyelinazation.
And not to get too technical, myelin, it covers exons. It helps nerves signals travel. And if your immune system takes apart the myelin, then the nerves don't work as well. And so, we get what we call auto-immune demyelinating disease. And so it's your immune system causing the nerves in your central nervous system to be damaged in that work as well.
This does not occur immediately. It's usually though within about two weeks of the rash. Once the rash is gone, you think you're out of the woods. The symptoms are really better. These folks then, a week or two after the measles, once they've recovered, will begin to have weakness, difficulty walking, sensory loss, motor loss, loss of bladder and bile control. And then this can actually lead to what looks like encephalitis where they get fever, headaches, stiff necks, seizures, coma, and death.
And all you can do during this time is support the person and hope that their immune system in this case settles down and stops causing the problem. But about 10 to 20% of those folks will also progress to death. And again, that's acute disseminated encephalomyelitis. It's your immune system causing a brain problem after you're all better from the measles.
And then we have really such as a sad case when this happens. It's called subacute sclerosing panencephalitis. And this occurs actually up to 7 to 10 years after measles infection.
So it's something that doesn't happen right away. It takes a long time, years after measles, and you have progressively fatal disease. Pretty much all the time, it's a fatal. And the incidence really depends on the age at which you had measles infection.
So overall, it's about 200 per million cases of measles. So this is rare but it does happen and it's a tragedy when it does happen.
If you had the measles when you were less than five years of age, then it's 730 cases per million cases of measles, which is about 1 in 1,367 cases of measles.
If you're less than 12 months old, so these are little babies who aren't even immunized against measles, so they're really the most at risk. If you're less than 12 months old when you get the measles, now your chances of these happening are much higher. It's actually 1 in 609 cases. About 1,640 cases per million cases of measles. But 1 in 600, I mean, that's a considerable risk. And this again is for folks who are less than 12 months of age when they get the measles.
And by the way, all these numbers where they're figuring out like one in a thousand, 1 in 600, these numbers are all based on measles outbreaks between 1989 and 1991. So this is an area of modern medicine, folks. It's not like, well, this happened one in a thousand back when we didn't have very good medicine.
This is now. This is for these little kids, 1 in 609 cases for this terrible subacute sclerosing panencephalitis. It's high risk for kids who are less than a year of age.
With this, it is a stage process, a stage one. You may not notice it. This may be a pre-school or elementary school-aged kid who just has a little bit of personality change. Maybe little more tired than usual, having some school difficulty, perhaps exhibiting some strange behavior. And this can actually last for a while from weeks to sometimes years. And often, providers may have trouble figuring out what's going on because it's not the first thing you think about.
Then stage two usually lasts a few months, typically less than a year. And you start to have muscle jerks and spasms of muscles, and dementia, just really cognitive decline.
And then stage three, further neurological deterioration, paralysis, rigidity.
And finally stage four, and this is pretty much 100%. If you get this thing, there's nothing you can do about it. And stage four then is a vegetative state. And oftentimes, these folks will get pneumonia or something like that because they're not up moving around, walking around, or they can get blood clots and die from it. This is really significant event.
Overall, the immediate death rate for measles is about one to two per thousand cases. Again, pneumonia and the encephalitis are the primary causes. Bacteremia and sepsis, which is overwhelming bacterial infection in the body, can also happen.
So once you get measles, what do you do about it? Well, as we mentioned, because it's a viral illness, supportive care is about it. So rest, fluids, control the fever trying to make folks comfortable. Deal with dehydration if it's happening.
Keep them away from others so they don't give measles to other folks.
And then, if they have a bacterial infection like a pneumonia or blood infection or bacterial meningitis, you certainly can give the antibiotics.
And then, treat any respiratory failure with oxygen supplementation. It can be intubated and mechanical ventilation if needed. If they're having encephalitis and seizures, using seizure medications. So really, just what we would call supportive care.
Now the other thing that is used in the treatment is vitamin A. So we want to give vitamin A supplements. It turns out measles often causes an acute vitamin A deficiency. And the reason this happens is the way that your immune system fights off measles requires a lot of vitamin A. The immune system uses up vitamin A as it's fighting the measles rubeola and that can then result in a vitamin A deficiency, which that vitamin A is important for the immune system to function.
And so, now that you're in a vitamin A deficient state, it can't work as well, so you have immune suppression. And then, you do have an increased risk of things like pneumonia, encephalitis, and bacterial infections on top of the measles because you're vitamin A deficient. Your immune system isn't working as well.
And so we do give vitamin A supplements to basically treat with vitamin A when folks have the measles. And then, you have to use the right dose because vitamin A is what we call a fat soluble vitamin. So you don't pee it out like you do vitamin C. A, D, E and K are fat soluble and those, actually, you store up in your fat and you can become toxic of that vitamin once the storage capacity is reached.
You have to use the right dose. This is not something you just do yourself at home. You do it under the guidance of a medical professional.
The other thing is using vitamin A is not going to prevent the measles, okay? It's not going to prevent it from happening. If your kids are unvaccinated or your child is less than 12 months and has not gotten their vaccine yet, giving megadoses of vitamin A is not going to prevent this.
You need the vitamin A as your body starts to use it up as it's fighting measles. But pre-dosing with Vitamin A is not going to prevent the measles from happening and can result in vitamin A toxicity if you're not careful.
So how do you prevent the measles? Well, one is to avoid contact with it if you're not immunized for whatever reason. But the biggest way to prevent it, of course, is with the MMR vaccine. And if you're able to get the MMR vaccine, we do recommend it. And we'll talk more about how that works and how well the protection is from it.
But not everyone can get the MMR vaccine. Those who are less than six months of age cannot have it. Between 6 and 12, you can get it but it doesn't count as one of your two that you need to get. And we'll talk more about that in just a few minutes.
But then, there are folks who can't have the MMR vaccine for other reasons because they have immunosuppression. Maybe they're on chemotherapy. They have cancer or they have an immune system problem to begin with. And we'll talk about why if you do have immunosuppression, why you wouldn't' want to get the MMR vaccine. We're going to cover all that in just couple of minutes.
But the main stay of prevention is MMR. Beyond that, avoid contact. And again, we treat with vitamin A but vitamin A is not going to prevent.
Hope that helps you with a little bit of a better understanding about the measles. I'm going to have a lot of links in the show notes for this episode. The CDC, the US Centers for Disease Control and Prevention has some really great information about the measles. And a lot of it is very readable for parents.
And so, I'm going to have a link to one of their pages called All About Measles. Another called Measles Vaccination. Measles Cases and Outbreaks, it looks at numbers and things. They're really some interesting materials. So be sure to check that out. Again, the links will be on the Show Notes for this episode, 431, over at pediacast.org.
We also have a 700 Children's blog post about measles called Measles Virus: Facts for Families. That will be a great one to share with your own online social media audience. We'll put a link to that in the show notes.
And then, healthychildren.org from the American Academy of Pediatric has some great resources, Measles: A Vaccine Preventable Disease, How to Protect Your Children During a Measles Outbreak, Protecting Your Baby from a Measles Outbreak FAQ. So lots of resources from the American Academy of Pediatrics about the measles.
So between our hospital here at Nationwide Children's, the CDC, the American Academy of Pediatrics, we have some great information. Also, a terrific op-ed in the Seattle Times by Dr. Kyle Yasuda, the president of the American Academy of Pediatrics. And I'll put a link to that in the show notes as well, over at Episode 431 at pediacast.org.
All right, let's take a quick break and then I'll be back. We'll talk all about the MMR vaccine. That's coming up here in just a moment.
Dr. Mike Patrick: All right, we are back and I want to turn our attention now toward the MMR vaccine. We sort of finished up talking about the measles in terms of prevention. And where I want to pick up is with the MMR vaccine. And I want to start with just a general review of how vaccines work.
It's a pretty simple concept at its base. And that is that you want to present the immune system with something that is safe and will stimulate the immune system to make antibodies against this thing. So when something that's similar but dangerous comes along, your immune system can fight it off.
And your immune system actually does this with every disease that comes along. Every little cold that you get, your immune system makes antibodies against it and then it retains a memory. So that then the next time that that particular virus comes along or other antigen, it is presented by those helper T-cells that we talked about when we were considering measles and some of the things that measles can do.
It decreases your helper T-cells ability to take antigens to other cells in the immune system and say, "Hey, look what I've found. Let's make antibodies against it." You kind of lose that protection when you have measles, the actual disease.
But what the vaccine wants to do then is to present something that's measles-like so that your body will make antibodies against it for memory. So that if the real measles comes along and those helper T-cells present the real measles, the immune system, it knows what to do. And it can make antibodies very quickly to protect you from the actual measles.
Now, there's a few ways you can do that. You can have just proteins that are on the outside of a particular microorganism and stimulate the immune system with those proteins. So you don't even really have the real bacteria or the real virus, you just have proteins. And the immune system makes antibodies against those particular proteins so that then when the real virus or bacteria comes along that has those proteins on the surface, then you can make antibodies very quickly and fight it off.
The problem with the measles is there aren't any proteins that have been able to be isolated that you could give just the protein and have a successful vaccine that makes good protection. It's just they're not been able to do that.
Another option is to kill the virus and inject the killed virus so it can't harm you, but your body can make antibodies against it. The problem is that killed viruses, the body knows it's dead. And it does not really stimulate the immune system to make antibodies against the killed virus, especially in terms of the measles virus.
So the only thing that works is a live virus. But we don't want to give you the measles. And so, you have to figure out a way to take the measles virus and what we would call it attenuate it. So we make it so that it's not as infectious as the real measles virus but you still get good stimulation of the immune system because it's still a live virus. It's just one that has been made safe or attenuated.
And the measles was first introduced as a live viral vaccine back in 1963. Mumps followed after that in 1967. And then, rubella or German measles was in 1969. These at this point were all separate vaccines, so you had to get a measles vaccine, a mumps vaccine, and rubella vaccine. All of them live viruses attenuated so they don't make you sick, but your immune system still creates antibodies against them.
And then in 1971, a combination vaccine was licensed and approved which had measles, mumps, and rubella all in it. And then in 2005, varicella, which is the virus that causes chickenpox, that was also added to some versions. So you can get a plain MMR that's measles, mumps, and rubella, but starting in 2005, they also had an MMRV which added the varicella or a chickenpox component, and that was began in 2005. So kids today either get the MMR or the MMRV.
And this vaccine is not injected into the bloodstream. That's not what happens. It gets injected subcutaneously. So this is just under the skin. And you have kind of a fat layer down underneath the skin.
It gets injected into that and then gets slowly absorbed. And your body's immune system engages and interacts with the live virus and makes antibodies against it. So when the real measles or the wild type of measles comes along, you have some protection.
Now, we're going to kind of focus right now just on the measles component of the MMR vaccine. We mentioned that in 1963, both killed and attenuated virus vaccine was made. They did try a killed vaccine against the measles. But again, in 1963 is when both the killed and the attenuated virus vaccines were out there. So, there were two different versions of the measles vaccine in 1963.
In 1967, the killed version was withdrawn from the market because it's just didn't work. Starting in 1967, we only had the attenuated virus.
But where did this virus come from? I'm kind of a history buff especially with medical history, so I always find this sort of thing interesting. John Enders and Dr. Thomas Peebles. John Enders was a microbiologist. Dr. Thomas Peebles was a physician.
And in 1954, they began collecting blood from several ill students during a measles outbreak in Boston. And they were tempting to isolate a sample of the living virus that they could keep alive. They had success, it turns out, from the blood of a 13-year-old by the name of David Edmonston.
And so, once they had David Edmonston's, his measles virus from his infection, this 13-year old, again 1954 in Boston, they created the strain of virus that would not infect people very easily at all but still make antibodies against it.
And then, 1963, they developed what was called the Edmonston B strain vaccine. And the Edmonston strain B, so they had attenuated this virus and again named after David Edmonston in 1963. It's nice that they give a nod to this kid's name.
The Edmonston B strain, that one, it wasn't the greatest. It wasn't as non-infectious as they would have liked it to be. It did not cause severe disease but a lot of people did have high fevers and even a measles like rash when they would get the vaccine. And so, as you can imagine, people didn't like this very much. And it turns out that that particular strain in the vaccine was withdrawn in 1975.
Scientists worked at further attenuating the same strain that directly came from, again, David Edmonston. But they're still messing with it, playing with it, attenuating it. In 1968, they came out with what's called the Edmonston-Enders strain of the virus. And that's actually the same strain that's used in the MMR vaccines still to this day.
And the Edmonston-Enders strain was first introduced in the MMR vaccine in 1971. And that's when they combined the measles, the mumps, and the rubella vaccine, all three of those attenuated viruses into one vaccine. They used this new and improved strain that didn't cause high fever and rash, again, in 1971.
Now, at that point in '71, it was just one dose of vaccine given at 12 to 15 months of age. In 1989, a second dose was recommended. And the reason for this is that when you give folks the vaccine, not everyone is going to what we call seroconvert. Not everyone is going to make antibodies against the virus, but it's really close to be in everybody.
So it turns out that if you do make antibodies against measles because of a live attenuated virus, so the MMR, it does give you lifelong immunity unless something harms your immune system. As long as you have a normally working immune system the rest of your life, you can expect lifelong immunity from the MMR vaccine.
Now, one dose given at 12 months of age gives you about 95% seroconversion. So if you gave all 12-month-olds one dose of MMR vaccine, 95% of them are going to have lifelong immunity. If you wait until 15 months of age, it's about 98%. So really close, but we still got a wiggle room 2, 3%. And it's not a hard firm 98% but it's close.
Now, so you give one dose at 12 to 15 months of age and you give the second dose at 4 to 5 years of age, so like before kindergarten. If you do that, then you're going to get 99 to 99.99% seroconversion. So you get really good coverage. That second dose doesn't boost it because if you made antibodies against measles, then again, you have lifelong protection as long as your immune system continues to be normal.
So that second dose is just as sort of change it from 95 to 98% seroconversion to 99 to really close to 100% seroconversion. Most people, 99 or more percent of people are going to make antibodies against MMR, against measles if you give two doses at 12 months and then again at 4 to 5 years.
So that's the reason that we do two doses, is to really protect folks lifelong and mostly everyone.
So to ensure protection, you do want to make sure that you've had or your children have had two documented doses after the age of 12 months. And most people do if you follow the standard immunization schedule. If you're not sure, if maybe you lost the records of your MMR vaccines, immunity can be tested with bloodwork. Or you can get another dose, if you don't know for sure, if you're an adult and you don't know. You can test your immunity, or you can just get another dose of MMR vaccine.
Babies as young as six months of age can receive the MMR but that does not count as one of their two doses. If they do get it, they'll be protected but they're still going to need another MMR vaccine at 12 to 15 months and again at 4 to 5 years. But it can be given younger if there's a lot of measles in your community and you want to protect your baby down to six months of age.
Now, folks who should not get the MMR vaccine, it's what we would consider contraindicated. If you have a severe allergic reaction, what we call anaphylaxis, after a previous dose of the vaccine or to any vaccine component in the MMR. And this is rare that this happens. It ends up being one in a million cases of vaccine where you have a very severe anaphylactic allergic reaction to one of components.
It is neomycin that typically will do this, which is an antibiotic in the vaccine. We're going to talk about the vaccine ingredients and components here in a couple minutes. But it's neomycin that most typically you would have an allergic reaction to. But again, this is not common. But it is the most common thing that can happen with the MMR vaccine.
And so if you have a history of anaphylaxis, very severe allergic reaction which happens right away or at least within a few hours, certainly not a couple days later, then that would be reason not to get the MMR vaccine.
Also, if you're pregnant, the measles virus, it's a live attenuated virus. It may not be safe for developing fetuses. And so, pregnant women should not get the MMR vaccine. Or if you have a severe immunodeficiency, that could allow that attenuated measles virus to be an issue if your immune system does not work normally, especially if it severely does not work normally. If you have a mild immune-deficiency, you might be okay. You'd want to talk to your immunologist about that.
But if you have the severe one, if you have a congenital immunodeficiency, if you're on chemotherapy or long-term immunosuppressive therapy, if you have an organ that you have a transplant or transplanted heart, or liver, or kidney and you're on long-term immunosuppressive therapy so that you don't have rejection of your new organ, that would be considered contraindication to getting the MMR vaccine.
HIV, if you are severely compromised with your immune system. Although if your HIV is controlled well and your immune system is not currently compromised, then you may be able to get it. Again, talk to your doctor where there's concerns there.
The big things are if you have an allergic reaction to a component in the vaccine especially neomycin, the antibiotic, or if you're pregnant or you have severe immunodeficiency, then you should not get the MMR vaccine.
And these people who can't get in then are really relying on their community not to give them the measles. That's one of the reasons that we have this concept of herd immunity that there are people out there who can't get the MMR vaccine.
There's also less than 1% of people who after two MMRs do not form good immunity against it. And you can argue maybe they did having immunodeficiency and that's why they didn't make a good antibody reaction against it. But these are the folks that we're really trying to protect by herd immunity or community protection so that you don't give people the measles.
Let's talk a little bit about some of the controversies surrounding the MMR vaccine. And I just want to talk straight with you. These are some of the things that people bring up and I just want to explore them a little bit more.
One is does the MMR vaccine cause autism? And this was has been debunked by multiple, multiple, very large well-designed prospect of studies. The study that show the connection was done by Dr. Andre Wakefield. And when you look at the details of his research, it was just terrible.
In fact, the journal that printed it withdrew the publication because it was bad science, not because they wanted folks to have the MMR vaccine and despite that it might cause autism. That was not it at all. It really was bad science and they retracted it once they discovered this.
The whole thing is really spelled out nicely by investigative journalist and New York Times best-selling author Seth Mnookin in his book called The Panic Virus: The True Story Behind the Vaccine-Autism Controversy. And I'll put a link to that book in the Show Notes for this Episode 431 over at pediacast.org. And I actually had him in the podcast studio awhile back for Episode 329. We called it the Vaccine War and we talked about what really happened with Dr. Andrew Wakefield.
It's crazy stuff. It involves this doctor drawing bloodwork on kids at his child's birthday party. And there was major conflicts of interest. It was just really should not have been printed to begin with and just bad, bad science.
And again, that book and that episode of PediaCast, we really delved in to the details. If you want to know more about that, be sure to check out PediaCast 329. Again, I'll have a link in the Show Notes for 431, The Vaccine War.
But anyway, suffice it to say, I don't think anyone respectable science person would say that MMR causes autism at this point based on very large well-designed prospective studies now that really have debunked that.
Another controversy surrounding MMR vaccine is that is does it contain fetal tissue? You may have heard this. Let's travel back to the early 1960s. There were cells from two terminated pregnancies that were used to grow live viruses for vaccines back in the '60s and the same cell lines are used today.
There are viruses that need human cells in order to grow. Viruses like the varicella virus, rubella, hepatitis A, one type of shingles, another type of rabies. And these viruses are still grown in the same human cells, the lines of which began in the early 1960s from two terminated pregnancies.
Measles viruses, as it turns out, they don't have to be grown in human cells. The measles virus today, they're not grown in these cells from fetal tissue back in the early 1960s. They're actually grown in a chick embryo cell cultures. It's chick embryos that the measles virus today. That still has same virus from our friend back in Boston, right? But they are not the same strain. But today, they're not grown in human cells from David Edmonston. They're grown in chick embryos.
Now, the MMR though does contain rubella. And rubella is grown in cells from those two terminated pregnancies back in the early 1960s. Those still use those cell lines, the rubella component of the MMR vaccine.
Now, the virus is separated from the culture. It's rinsed. It's separated from the medium that it was grown in, but fragments remain. You can't get rid all of it. And so could there be some human DNA remains from those two terminated pregnancies in the MMR vaccine because that's the cells that they were grown in? Could there be some human DNA?
As it turns out, probably yes. There probably is a little bit of human DNA in the MMR vaccine but we're talking a nanogram. We're talking 1 billionth of a gram. So this is very, very teeny tiny amount of human DNA.
And as it turns out, there's human DNA on most of the things that we come in contact with and including what we eat and drink. Fruits and vegetables probably have more than 1 billionth of a gram of human DNA remains just from the people who pick the fruits and vegetables and pack them up for you. Even if you rinse some, you still can have a billionth of a gram easily on it.
I certainly respect ethical and religious beliefs about this. Some folks would say, "Well, I don't want to endorse terminated pregnancies being used." You know my thoughts on this, and I'm not saying you have to have the same thoughts, but just my thought process is what a legacy for these two fetuses that were terminated if you consider that their cell lines are still used to this day to grow rubella virus.
Rubella, as it turns out, is a devastating disease to fetuses. Before the MMR vaccine, there were about 5,000 miscarriages every year from congenital rubella in the United States. And if you consider that that vaccine has been used for 50 years now, these two terminated pregnancies have resulted in 250,000 saved lives by preventing congenital rubella in other babies.
From an ethical standpoint, the deaths of these two fetuses in the early 1960s, as tragic as that may be, it has led to an overreaching good that has saved many, many, many lives over half a century. Do you throw that good away and deny your children protection because of where it came from?
Each can decide from themselves. I'm just trying to get across where my mindset is with this. I say, "No, you don't throw it away. And I wouldn't deny their legacy for my kids." But again, you may feel differently about that.
The other controversy surrounding the MMR vaccine is the ingredients. What ingredients are in it? Here are the ingredients. This is what's inside the MMR vaccine. They are the attenuated viruses, so we have measles, mumps, and rubella, live viruses but made safe. We have sorbitol which is a sugar. We have sucrose which is a sugar. We have sodium chloride which is salt. We have sodium phosphate.
And these things are there, especially the sodium chloride and the sodium phosphate. When you're injecting something into the body, you want it to be isotonic. And if you remember back like the high school biology class, there can be hypertonic and hypotonic and water moves from where there's less particles to where there's more particles.
And so you want something that you're injecting into and under the skin to have the same osmolarity as the surrounding tissues so water doesn't travel back and forth. And so that's the reason that has some of these things in there.
It also has hydrolyzed gelatin which is part of the culture medium. It has recombinant human albumen, that's from the rubella. It has egg protein, that's from measles. And mumps is actually grown in calf serum, so there's a little bit of fetal bovine serum but it's less than 1 part per million. And that's because of the mumps virus.
And the neomycin, we talked about that when we talked about anaphylaxis and allergies. It's an antibacterial and it's there to keep bacteria out of the MMR vaccine because it's got sugar in it. And you don't want bacteria growing in the shot itself and then clearly they're injecting dangerous harmful bacteria into your child. So there's antibiotic in there to kill any bacteria that makes its way in.
And then there's some buffers and other media ingredients that were part of the culture that you can't rinse off 100%.
And so that's it. That's what's in the MMR vaccines. There's no mercury. There's no aluminum. There's no formaldehyde.
Now, some other vaccines do have those things. And while I got your attention, I just want to mention something about those. Mercury was in vaccines that were in multi-dose vials and it is still in some multi-dose vials of flu vaccine. Most kids, we give single dose vaccines where the syringes has one dose of the influenza virus in it.
But in adults, we do still use some multi-dose vials, so you have more than one dose. And in those, you really want something that's going to kill anything that could get in there that's not supposed to be there. And thimerosal is a form of ethylmercury that is very good at killing anything that gets in there.
Now, that's not the same as metal mercury. And metal mercury is the kind of mercury that you hear about in tuna fish. It's the more dangerous mercury, the one that's in thermometers. That is a dangerous substance.
But ethylmercury has never been shown in the doses that it was given, even when it was in all the vaccines, was never shown to actually cause toxicity in practice. But it was removed because parents were concerned about this. There was a big uproar and they didn't want that to be a barrier.
Sometimes, we do things just to please what's out there without necessarily having been dangerous, but we don't want to create barriers that people worry about. And so, the thimerosal was taken out of all the vaccines just in case, even though it never was really shown to be a problem. But there is no mercury or thimerosal in the MMR vaccine.
Aluminum in a very tiny amount improves the stimulation of the immune system or that seroconversion. It makes it more likely that you'll form an immune reaction when the aluminum is present with some antigens. The MMR vaccine, as it turns out, it doesn't need aluminum in it in order to form a really good immune response. You don't need that.
There are some other vaccines that do need that, but it's a very tiny amount and there is no evidence that that causes neurotoxicity or any problems at all in the vaccines. There's no evidence to suggest that.
And then, finally, formaldehyde, that's used to kill viruses, so like the poliovirus as it kill virus vaccine. It can also detoxify bacterial toxins like diphtheria, so the DTP and the TDAP. Those have a little bit of formaldehyde in them because it's used to make it safe.
Now, it's a very small amount. Your body as it turns out makes its own formaldehyde in small amounts. Formaldehyde is found in food and most notably in pears. And none of these vaccines, by the way, go directly into the bloodstream. They're either subcutaneous or intramuscular. And they get put into the muscle. None of them go directly into the bloodstream. Sometimes you hear that, too.
So there's a reason that some vaccines have mercury, aluminum, and formaldehyde. There's a reason for them. It's a small amount and the good and the benefit certainly outweigh any... I don't even think there really is any risk associated with those. But, okay, let's say there is like a tiny little teeny teeny tiny bit of a risk, the benefit far outweighs that.
If you're more interested in common ingredients in US licensed vaccines, not just the MMR but all of them, you want to see the complete list of everything, I'll have a link for you in the show notes for this episode, 431, over at pediacast.org.
Another thing that you'll see with vaccines, side effects. There are some side effects. You can get soreness and redness at the injection site. And a low fever and a mild rash are also possible. Not to the degree of that original measles virus, but it can still sometimes happen.
And this is your immune system at work. It's not that your child has the measles. It's your body's immune system is making antibodies against it, so that when the real measles comes along you're prepared. And the by-product of your immune system in action can be a little bit of a fever and a mild rash but they're not dangerous. They're not concerning.
Okay, so what about complications? What kind of complications can we see from the MMR vaccine? Well, some kids will have a little bit of a higher fever. And we know that when you have a rapid change in your body temperature, that can cause a febrile seizure.
And so, as your immune system is at work dealing with the MMR vaccine, making antibodies against it, for about one to two weeks after you get the MMR, you are at an increased risk for a febrile seizure, which a lot of kids have this. They're scary to see but they're not life threatening. They're not dangerous in any way, simple, febrile seizures. And it ends up being about 1 in 3,500 doses of the MMR vaccine who are younger than age seven. So if you're less than seven and getting the MMR vaccine, about 1 in 3,500 could have a febrile seizure.
Another possibility is that your immune system can attack your platelets. And so, you can get transient or temporary low platelets. And there's a risk of that happening for about six weeks after the MMR vaccine. Where, again, your immune system is stimulated in such a way that you make antibodies against platelets but only temporarily. And that can cause low platelets and easy bleeding.
But the risk of that is 1 in 40,000 doses. Okay, again, 1 in 40,000 doses, you can see that happen. And that recovers on its own. There's no treatment for it. You don't need to do anything for it. It's just gets better.
And then, we talked about anaphylaxis from the neomycin in particular. That's about one in a million doses that you see that.
And then, remember those things that the wild type measles? So real measles can cause encephalitis, acute disseminated encephalomyelitis and subacute sclerosing panencephalitis. We talked about those in the first part of today's episode.
So because this is a live virus and someone's immune system maybe is not working. They haven't been diagnosed with an immune problem or maybe they have one that's not been diagnosed. There have been a handful of cases reported in vaccinated individuals where they can get these things happening, encephalitis, the acute disseminated encephalitis and subacute sclerosing panencephalitis.
But we're talking like one case and hundreds of millions of doses. And it's actually more likely that they actually were exposed to a wild type measles virus but because they have the measles vaccine, they did not respond to it. They did not make protection. And when they were exposed to the real measles virus... Maybe they had measles that was diagnosed to some other viral infection that didn't get diagnosed as measles.
Or maybe they formed partial immunity and so they were sort of protected. And it didn't look like real measles, it look like some other virus. But it was real measles because their immune system only partially protected them. And then, they ended up with these things.
It is possible but it's extremely, extremely rare. And we're talking again to the tune of one per hundreds of millions of doses. And, as it turns out, only one case ever, one case where someone had one of these brain infections was it definitively linked bank to the Edmonston-Enders strain that's in the MMR.
Now, on the other hand, how many cases of encephalitis, acute disseminated encephalomyelitis and subacute sclerosing panencephalitis, how many cases of those things has the MMR prevented in the past 50 years? So even if the MMR did cause one per hundred million doses of these things, when you consider how many cases that it prevented, then you're looking at, "Hey, it's worth it."
It's worth that one in a hundred million, probably even rarer than that, risk compared to taking your chances with the real measles virus. And again, compare all these numbers we're talking about to the death rate from measles, 1 to 2 deaths per 1,000 cases even with the best modern medicine. One in a million chance of a severe complication like anaphylaxis or severe allergic reaction with MMR versus one in a thousand chance of death with the actual measles disease.
So I can't speak for your risk tolerance. Mine swings widely in favor of getting the MMR vaccine. And if you're worried about that one in a million chance, you should be even more worried about your children around swimming pools and playgrounds and strapping your child into a car and speeding down the highway at 70 miles per hour.
When you really look at benefit versus risk, I think that the benefit of the MMR vaccine which, again, measles can cause 1 to 2 deaths per 1,000 cases, the benefit outweighs the risk, which of a serious complication is going to be one in a million and probably even less in the real world.
What about VAERS? What about the Vaccine Adverse Event Reporting System? That's a great question. Basically anyone, any physician, medical provider, parent, anyone can get on there and say, "Hey, my child had a vaccine and then this happened."
It does not show any causative effect and when you have something happening with the frequency the vaccines happen, of course, you're going to see other things that seem to be associated. They're associated in time, but they're certainly not cause and effect.
And anything can be reported by VAERS. I mean, you can report that you were stung by a bee after you had the MMR vaccine. If literally, if you go there and look, it's all there for folks to view, you'll see that there's all kinds of stuff that can be reported, but again, it doesn't mean cause and effect.
What about vaccine court and the National Vaccine Injury Compensation Program? The reason that those are on places, there's going to be people who say the vaccine cause this issue even if it didn't. And there's going to be juries that would award crazy amounts of money without any evidence if that's really a cause issue.
And so in order to keep those out of courts where decisions can be made, not based on science but based on emotions, the vaccine court was created and the National Vaccine Injury Compensation Program was created to say, "Okay, you've got a concern. We don't really think it's cause from the vaccine but we're going to compensate you regardless and still do the greater good of keeping the vaccines around."
And you can imagine if those sort of things did not exist, there would be lawsuits and there would be no reason for businesses to create vaccines. It would just be too big of a liability. And so, in order to protect the greater population against something that science says is safe and good, these are sort of necessary components of that system of being able to keep us. I hope that makes sense.
A couple other links that we're going to have in the show notes that I think would be interesting and helpful for you, MMR Vaccination: What Everyone Should Know from the CDC, and MMR Vaccine: What You Need to Know from the American Academy of Pediatrics. And I'll put those links also in the show notes.
Dr. Mike Patrick: We are back with just enough time to say thanks once again to all of you for taking time out of your day and making PediaCast a part of it. I really do appreciate you stopping by.
We have lots of links in the show notes for you this week. All About Measles, Measles Vaccination, Measles Cases and Outbreaks, all from the CDC; Measles Virus: Facts for Families from the 700 Children's blog.
Measles: A Vaccine Preventable Disease, and How to Protect Your Children During a Measles Outbreak, Protecting Your Baby from a Measles Outbreak FAQ, that's all from the American Academy of Pediatrics.
A Regrettable Milestone in the Measles Epidemic, that was an op-ed from the president of the American Academy of Pediatrics.
PediaCast 329 where we talked about Seth Mnookin about his book, that one's called The Vaccine War. I think you'd find that one interesting.
The Panic Virus: The True Story Behind the Vaccine-Autism Controversy, that's the book by Seth Mnookin. I'll have a link to that in the show notes.
Common Ingredients in U.S. Licensed Vaccines, and the MMR Vaccination: What Everyone Should Know, and the MMR Vaccine: What You Need to Know from the CDC and the American Academy of Pediatrics, respectively. All those links in the show notes for this episode, 431, over at pediacast.org.
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