Childhood Vaccines – part 1 – PediaCast 351

Show Notes


  • Dr Michael Brady joins Dr Mike in the PediaCast Studio for a two-part series on childhood vaccines. Today we cover Hepatitis B, Diphtheria, Tetanus, Pertussis, Hib, Polio, Rotavirus and the Pneumococcal vaccine. We also explore how immunizations work, talk about herd immunity, and walk through a risk/benefit analysis of the vaccine decision. We hope you can join us!


  • How Vaccines Work
  • Herd Immunity
  • Immunization Benefits
  • Vaccine Risks
  • Hepatitis B Shot
  • DTaP / TdaP / Td
  • Tetanus Shot
  • Diphtheria
  • Tetanus
  • Pertussis
  • Whooping Cough
  • Hib
  • Haemophilus Influenza type b
  • Polio
  • Rotavirus
  • Pneumococcal Vaccine




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's 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's August 31st, 2016, Episode 351. We're calling this one "Childhood Vaccines Part 1". I want to welcome everyone to the program.  

I do have a big show for you this week. In fact, it's so big that one episode is not going to contain it. So right out of the gate, we're dividing the material into two episodes because there's a lot to cover as we consider childhood vaccines. Now, little bit of background for you, we haven't really done a survey of all of the childhood immunizations in ten years of PediaCast episodes. We've talked about specific vaccines before. We'd answered many of your questions about certain ones. We've covered plenty of news stories on immunizations in the past.

We even had Seth Mnookin in the studio talking about his book, The Panic Virus: The True Story Behind the Vaccine-Autism Controversy. Seth by the way, is a New York Times bestselling author and investigative journalist. He did a lot of digging to uncover the event surrounding Dr. Andrew Wakefield's proclamation — false proclamation — that the MMR vaccine was associated with autism back in the late 1990s. 


Of course, now we know Dr. Wakefield's work was largely fraudulent. There is no association between the MMR vaccine and autism. Significant conflicts of interest were exposed. The journal Lancet retracted the study. Dr. Wakefield lost his medical license and multiple large well-designed studies since that time have not or have failed to show an association between any vaccine and autism. 

So, interesting stuff and definitely a major event in medical history that still influences and affects many families today. If you want to learn more about the details surrounding that story, you want to listen to my interview with Seth, PediaCast 329. "The Vaccine War" is what we call that one. And I'll put a link to it in the Show Notes for this episode, 351, over at PediaCast. org. 

So, we focused in the past on individual vaccines. We've covered some of the controversies. I've done my best to convey to you over the  years why it is that I believe the benefits of immunizations far outweigh the risks and why the vast majority of children should be vaccinated according to recommended immunization schedule.

But what we have not done in the past is to look at the big picture of childhood vaccines. We haven't done a nuts-and-bolts sort of approach like we have for so many other child health topics. So, over the course of the next two episodes, that's what I wanted to do, sort of a one-stop or two-stop, as the case may be, approach to childhood vaccines for those looking for comprehensive evidence-based information on the topic. 

So the plan is to cover all of the routine childhood immunizations and the diseases they prevent. Now, I know you get the vaccine information sheet with each shot, right? So you already know a little about each vaccine and its corresponding disease or diseases. But I wanted to expand that into a little more detail. What do these illnesses actually look like, what sort of symptoms and complications did children of the past suffer? Would these illnesses still be dangerous today given modern medicine and improvements in supportive care? 


In other words, do we still need to prevent these diseases? How do the shots work? Are we giving too many shots? Can our immune system handle a bunch of shots at one time? What are the real dangers of immunizations and how does one walk down the risk-benefit road that we talk about so often on this program as that journey pertains to childhood vaccines?

Also, herd immunity, it's a term you've probably heard but what exactly does that mean? So we'll answer some of these questions today. The remainder will answer next time as we cover Part 2 of Childhood Vaccines. 

We'll start here in a few moments with the first shots that young children encounter. So, we'll cover hepatitis B, DTaP, which is diphtheria, tetanus and pertussis. And we'll also cover different versions of these immunizations, one given to older children including the Tdap — another one, just the big T little d — or just regular plain tetanus shot. 

We'll also talk about Hib (which protects against Haemophilus influenzae type b), polio, rotavirus and the pneumococcal vaccine, along with the diseases that these shots prevent. So again, hepatitis B, diphtheria, tetanus, pertussis or whooping cough, Haemophilus influenzae type b which is quite a bit different than the flu, even though the word influenza is in the name. We'll also cover polio, rota virus and the many dangers of streptococcus pneumonia. 

So lots coming your way today. And then, next time in Part 2, we'll hit influenza, the real flu, MMR, varicella or chicken pox, hepatitis A, the meningococcal vaccine — or meningitis vaccine as it sometimes called — and the HPV. So it's a lot to cover, I know, but moms and dads have lots of questions and I really wanted to create a couple of episode where you could find answers in one package. 


Of course, in our usual fashion, I have a fantastic guest lined up to help me with the task. Dr. Michael Brady is a pediatric infectious disease expert at Nationwide Children's. He has served as past Chair of the American Academy of Pediatric Committee on Infectious Disease and associate editor of The Red Book, which as fellow health care providers in the audience know is the go-to infectious disease reference in the world of pediatrics. So, in other words, we have an infectious disease and childhood immunization superstar joining us today. 

Before we get to Dr. Brady, I do want to remind you, it's easy to get in touch with me. If you have a question you'd like me to answer or a topic you'd like covered on the show, just give me a holler. It's easy to do. Just head to and click on the Contact link. You can also call the voice line at 347-404-KIDS. 

Also, I want to remind you, the information presented in PediaCast is for general educational purposes only. We do not diagnose medical conditions or formulate treatment plans for specific individuals. So, if you have a concern about your child's health, be sure to call your doctor and arrange a face-to-face interview and hands-on physical examination.

Also, your use of this audio program is subject to the PediaCast Terms of Use Agreement which you can find at 

All right, let's take a quick break. We'll get Dr. Michael Brady settled into the studio and return to talk about childhood vaccines. That's coming up, right after this.



Dr. Mike Patrick: Dr. Michael Brady is an infectious disease specialist at Nationwide Children's Hospital and a professor of Pediatrics at The Ohio State University College of Medicine. He served as Chair of the Department of Pediatrics at Ohio State from 2005 until 2013. And he's also past Chair of the American Academy of Pediatrics' Committee on Infectious Disease. 

Dr. Brady is currently an associate editor of the Red Book, which is the comprehensive infectious disease reference from the AAP. And he's a candidate to be the next president of the American Academy of Pediatrics.

You won't find a more qualified guest to talk about childhood vaccines and the diseases they prevent. So, let's give a warm PediaCast welcome to Dr. Michael Brady. Thanks for joining us today. 

Dr. Michael Brady: Thanks for having me. 

Dr. Mike Patrick: Really appreciate you stopping by. So running for president of the American Academy of Pediatrics, certainly exciting. And we're going to talk more about that from the American Academy of Pediatrics National Conference and Exhibition in October of this year, 2016, in San Francisco. PediaCast and myself will be podcasting from the Nationwide Children's booth in the exhibition hall. We're going to talk to Dr. Brady about the state of pediatrics today during those interviews — what are the most pressing challenges for doctors and parents and kids, what can we do to meet those challenges. So stay tune for that. 

By the way, if you're a pediatric provider and you're attending the AAP conference in October in San Francisco, be sure to stop by the Nationwide Children's booth and say hello. And if you like, we can get you on the podcast, sharing your joys and challenges as a pediatric provider. We'll record some special shows, hopefully featuring lots of you — the pediatric providers in the crowd — from the convention hall in San Francisco again in October. So hopefully you can join us. 

So, let's get to it with Dr. Brady because we have a lot to cover today. I think, as we think about childhood vaccines, a nice starting place is just an explanation of how vaccines work. 

Dr. Michael Brady: So, vaccines are a biological product that are designed to prevent diseases by prophylactically or sometimes therapeutically, stimulating the body's own immune response to the different diseases. So that if somebody becomes exposed to one of these diseases, the immune system has already developed the ability to protect the individual from whatever the disease is. Most vaccines are currently addressing issues of infectious diseases, but vaccines can be considered for a lot of other things and there's a lot of interest in trying to develop vaccines for cancers even. 


Dr. Mike Patrick: So with regard to childhood vaccines, we're trying to make memory with the immune system and providing a safe way for the immune system then to remember when the actual disease, whether it's a virus or bacteria comes along, that the immune system gets revved up and will fight that because it has memory for it from the vaccine that we gave. Is that a pretty accurate summary?
Dr. Michael Brady: That's very accurate summary. And again, one of the advantages of the vaccine is it tries to develop this immune response without having the patient or the person actually have to undergo the disease. So it's a much safer way to develop protection. 

Dr. Mike Patrick: Now, one of the things that folks hear about with regard to the benefit of vaccines is not only that it helps to protect the individual child but there's this also concept of herd immunity. What exactly is that? 

Dr. Michael Brady: Actually, we're trying to move from the term herd immunity to community protection.

Dr. Mike Patrick: Because it's a better description of what's happening. 

Dr. Michael Brady: Right. And so, what happens is most of these infectious diseases that we're considering are transmitted from person to person. So you can reduce kind of outbreaks if you have very limited numbers of people who are capable of transmitting the particular virus or the bacteria to another individual. 


So the concept of community protection is you have to have a certain level of individuals who are protected so they can eliminate further transmission. And a very good example is what happened at Disneyland last year with measles. Measles is one of the most contagious diseases that we have, and there were a number of people at Disneyland who hadn't been immunized. They were exposed to measles, developed measles. And, unfortunately, many situations where these people were not immunized, they were coming from communities where there are clusters of other people who were not immunized against measles. 

And so we had many pockets of outbreaks that were related to the fact that the number of people in the different communities was at such a low level of being vaccinated that they were able to continue transmission. But it didn't actually get transmitted very much in other areas around the country because we did have this community protection with enough people who were immunized against measles. 

And this is particularly important because we have some of our children who are either too young or because their immune systems are not strong enough, unable to either respond to the vaccine or get the vaccine. And one of the things we would like to do is make sure that there's enough people in the communities that are immunized, so they can protect these kind of more vulnerable children. 

Dr. Mike Patrick: Because if the other folks are immunized, then you have fewer people to get the disease from, which makes it safer for those kids. Now, one of the folks that we're trying to protect with this are those who can't get immunizations — so if they have cancer for instance or other immune problems and they can't have vaccines. But also, sometimes vaccines don't work in these specific individuals. Is that correct? 


Dr. Michael Brady: So, no vaccine is perfect. What happens is the vaccine is designed to try to stimulate the immune system. And there are some children whose immune systems may not be able to respond to the particular vaccine when it's given. So, we have some children with immune deficiencies. We may have some children who are on medications that alter the immune system. Most people think about cancer patients and chemotherapy but probably one of the more common medications would be some of the corticosteroids like prednisone, which can influence the ability of the immune system to respond. So we have some children who can't respond to the vaccines because their immune system — either naturally or through the use of medications — is modified. 

But the other things is we have some children who are too young to respond to certain vaccines. And so, under those circumstances, again, we would like to make sure that the people that are around them kind of cocoon them and protect them. 

Dr. Mike Patrick: And it can even be in healthy individuals where you don't have 100% what we call zero conversion from the vaccines. It's a rare occurrence but you just don't know if your kid is one of the ones who didn't convert. So, even if your child has had vaccine and seems healthy, it's still nice to sort of cocoon them with folks who are immunized so they don't have someone to get the disease from. 

Dr. Michael Brady: Right. And again, a good example is the measles vaccine where we know that about 95% of healthy children who receive the vaccine will developed protection, but that means that 5% won't. And when you have four million children every year being immunized, that becomes a large number over time. 


And we did find out in the late 1980s that we needed to immunize with the second dose to try to get to that 5% because we had a kind of outbreak of measles in the United States that was occurring because we did have that 5% who are unable to respond or didn't respond for some reason. And now, again, we've been able to control measles by using two doses. 

Dr. Mike Patrick: And I think in terms of covering childhood vaccines, we've talked about the benefits of vaccines, and protecting kids from these diseases in a way that they don't have to get the disease first, and protecting whole communities with the community protection or what is called herd immunity. Let's discuss real quick before go through the vaccines' actual risks because we want to be transparent about what the real risks are. Sometimes, physicians sort of get blamed for skirting over any risks that are associated with immunizations and just trying to push them. 

I want to just take a step back and address what the risks are and then put that into perspective and then we'll compare risks and benefits as folks are making decisions about vaccines. 

So I think first risk would be allergic reactions to the components, but this isn't something that you see very often, correct?

Dr. Michael Brady: No. Fortunately, actually, as you mentioned, the vaccines contained not only the agent that you're trying to immunize it against but also some other chemicals for stabilization and trying to avoid contamination. And so, people can be allergic to those, but those probably occur less than one in a million immunizations. So they are something we have to aware of. And if a child does develop an allergic reaction to a specific vaccine, we have to be very careful that other vaccines that may have similar components are not given to that child. 


Dr. Mike Patrick: Another thing that some folks will come across in reading or researching vaccine is something called Guillain-Barre syndrome. And if folks want to know more about this, you can do a Google search for PediaCast and Guillain-Barre. So we've covered this in the past. But this is also something that can happen after the influenza vaccine in particular, but it's still one in a million kind of situation, correct? 

Dr. Michael Brady: The Guillain-Barre syndrome was kind of first identified as a potential adverse event associated with immunizations back in 1976 with the initial kind of swine flu influenza vaccine. For the most part, that was the only year where there was a significant amount of Guillain-Barre associate with administering the influenza vaccine. Most other seasons with exception of maybe one or two, there really hasn't been any significant relationship between influenza vaccine and Guillain-Barre.

But again, since you're using a biological product to try to stimulate the immune system to provide protection, and Guillain-Barre is kind of an immune-mediated phenomenon, it is something that the Centers for Disease Control and the FDA are very interested in and make sure that there's adequate monitoring kind of post-licensure experiences of people who receive vaccines. And so, Guillain-Barre is really something that we recognizes the possibility. It has happened very rarely but it is something that is constantly being monitored to make sure that we can understand whether or not it is a real affect or not.


A good example, in 2005, when the first meningococcal conjugate vaccine became available, there were reported to VAERS (which is kind of a passive reporting system) a number of children who'd received the vaccine who got Guillain-Barre syndrome, After further kind of evaluations, it was determined that these were just temporarily related and not causally related to that vaccine. In other words, Guillain-Barre does happen in otherwise healthy people. And it just so happen that these healthy people who got Guillain-Barre also got the vaccine, but there was no relationship. And that was determined by looking at large databases of children who did and did not receive the meningococcal conjugate vaccine.

And it actually turned out that in that particular large study with more than 20 million adolescents, that Guillain-Barre actually occurred more frequently in those who didn't get the vaccine. Now, the vaccine certainly should not protect you from Guillain-Barre but it does suggest that it was not associated with the vaccine. 

Dr. Mike Patrick: And we've talked about this on PediaCast many times. Just because two events are associated in time doesn't mean that one caused the other. 

You mentioned VAERS, which is the Vaccine Adverse Event Reporting System. And this is just a system that anyone can report any event following a vaccine, but it certainly doesn't mean that the vaccine caused any of those events. 

Dr. Michael Brady: Yeah, that's definitely true. So VAERS is kind of like your early warning system. And what we want is for people to provide any kind of information on any kind of an adverse event that occurs following the administration of a vaccine. And as you mentioned, it does not necessarily mean that there's a cause and effect, but it does require then additional evaluation to try to assess whether there is a cause and effect.


And so, again, VAERS is something that we want people to actively submit information to, but then there's other kind of mechanisms. So there is VSD, which is the Vaccine Safety Datalink Network, where they have a large number of people that they can monitor on a more prospective basis and that can either support or refute a connection between a particular adverse event and the vaccine. 

Dr. Mike Patrick: Sometimes those numbers get reported as "Oh, look, vaccines are causing all of these things," and those numbers from VAERS are reported. So a parent who comes across this information that looks like the vaccine is causing every single one of these things. But a lot of the time when the studies are done and folks look into it, that's not the case at all. 

Dr. Michael Brady: Yeah, that's right. 

Dr. Mike Patrick: There's another condition folks will come across. And this one can be devastating, called sub-acute sclerosing 
anencephalitis, that sometimes you'll see out there as associated with the measle vaccine. But the association is really with more the wild measles virus rather the vaccine itself. Is that correct? 

Dr. Michael Brady: That's very true. So one of the conditions that was fortunately very rare but was seen after natural measles was, as you mentioned, SSPE, the sub-acute sclerosing panencephalitis. But, again, because we're giving a live virus with the measles vaccine, there has been tremendous interest to try to assess whether or not this was a complication of giving the live measles virus as part of the vaccine. 


There is very good data to support the fact that sub-acute sclerosing panencephalitis is not associated with receiving the live measles vaccine, but it is associated with measles. So that gives us one more reason to actually use the vaccine. 

Dr. Mike Patrick: And as it turns out, it's like 1 case per 17 million people. So, this is even more, not even one in a million — it's much rarer even than that — but again, I wanted to mention it because folks will come across that as they're looking into these things. 

And then another is mercury. So, thiomersal was a preservative in multi-dose vials of vaccines to help prevent bacteria from contaminating the vial. But for the most part, vaccines are single-served now and do not contain thiomersal. Is that correct? 

Dr. Michael Brady: That's correct. The only vaccines in the United States that still may thiomersal  are the multi-dose vials for the influenza vaccine. And multi-dose vials for influenza vaccine are particularly viable when you're trying to have large numbers of people immunized at one particular location. But that's the only current vaccine in the United States. 

However, around the world, there are still many vaccines that contain thiomersal. And the important thing that you need to understand is  people get concerned about mercury poisoning, and they have good reason to, but that's methyl mercury, which accumulates in the body. Thiomersal is ethyl mercury which can be metabolized, and therefore does not accumulate in the body. And there really is no evidence that thiomersal has caused any adverse consequences in any of the children who are immunized. 

However, it was removed from the vaccines, not because there was a concern that it was harmful. There was a concern that it was reducing acceptance of vaccines. And in order to try to enhance people's acceptance of vaccines, it was removed in the United States. 


Dr. Mike Patrick: So we just didn't want to give folks another reason to be concerned, even though that really wasn't a concern. 

Dr. Michael Brady: That's right.

Dr. Mike Patrick: And as I recall, when they first went to taking the thiomersal out of the vaccines, there were shortages in lots of the vaccines because the production to make all these single-serve ones was kind of lagging behind. Of course, that's not an issue now, but I remember that was a consequence of taking the thiomersal out, that there were some unprotected kids because there were shortages of vaccines there for awhile.

What about specific additives to vaccines? Why is aluminium in immunizations? 

Dr. Michael Brady: So, sometimes, when you're trying to stimulate the immune system, you may need to have some kind of a chemical that can jumpstart the immune system, and that's called an adjuvant. Aluminium, it turns out, in certain aluminium salts is a very good adjuvant. That means that with a smaller amount of whatever the vaccine component is, if you add the adjuvant, you can get a much stronger immune response. And that's very valuable — when you're getting exposed to a particular pathogen — for the immune system to be really robust and be able to respond very rapidly and very strongly against the agent. 

So there are certain vaccines that contain these adjuvants, and there is no question that they make the vaccine a much better vaccine. Now, again, because you're adding some additional chemicals, the people who create the vaccines and then all the people that are responsible for monitoring the vaccines are constantly trying of evaluate whether or not there is any evidence that adding any of these chemicals might be causing problems. 


And, to date, there's no evidence to suggest that they are causing a problem. One of the nice things is that the Institute of Medicine, which is probably the premiere organization trying to look at immunizations and any potential harm, has come out and said that they currently don't have any evidence that any of these additional or adjuvant chemicals are causing problems for children. 

Dr. Mike Patrick: Other additives that folks will come across — formaldehyde or formalin in trace amounts, and that's used to inactivate the virus for some viral vaccines, correct? 

Dr. Michael Brady: Yes. Again, what we're trying to do is stimulate the immune system without having to expose somebody to potential harmful organism. And so, yes, some of the vaccines are taking the live organism and killing it with formalin. But then, the process is continued where they try to remove as much formalin as possible, and it usually ends up being in trace amounts and far less than what you would be exposed to in almost daily activities. Because, like it or not, we get exposed to formalin in a lot of things that we eat and experience on a daily basis. 

Dr. Mike Patrick: So these things do have purpose. It makes sense and helps the vaccine to work. Also, antibiotics, anti-fungal in trace amounts to prevent contamination of certain vaccines. But again, none of these things have been shown to be a problem and if a problem does arise we have this early warning system in place to evaluate. And as we go through the individual vaccines, there had been times when vaccines have been removed from the market or when change has been made because we have seen that there are issues. 


So it's not just a "Gung-ho, we're going to do this without really being thoughtful and watching for issues and then reacting to issues when they do occur." 

So let's walk through just real quick, when you do have parents who are concerned about these things that we've talked about, how would you walk through sort of the risk-benefit analysis for vaccines? I think most pediatricians and most parents are going to expect the most pediatricians are going to say the benefits far outweigh the risks. Would you agree with that? 

Dr. Michael Brady: Oh, I definitely would agree with that. And one of the, I think, major challenges to the pediatrician in 2016 is that many of the diseases that are being prevented have been prevented for such a long time that many parents have no understanding of the real potential impact of these diseases. And so, that's probably the biggest challenge when you're trying to discuss the difference between the risks and the benefits, is that if they don't understand what the benefit is, any risk may be unacceptable. And I think that's one of the major challenges — is to try to make it very clear that many of these diseases could happen again if we don't immunize and that many of them are very, very serious. 

People discuss the issue sometimes that why get the chicken pox vaccine. I mean, chicken pox is not that big of a deal. And yet, if you were to look at what happened prior to the availability of the vaccine, there were hundreds of deaths related to varicella. Children will get varicella encephalitis. There will be significant cellulitis when they got infected and they were very difficult to treat. So the average child may have a benign disease but there were actually some significant consequences. So it is kind of a challenge trying to get people to understand that the benefits are truly outweighing the risk. 


Dr. Mike Patrick: And when it's your child who gets encephalitis from chicken pox, and especially if you had intentionally exposed them to chicken pox and then that happens, just really tragic. And that sort of thing did happen. 

So let's kind of go through the childhood vaccines that kids get right out of the gate. So the first one in the hospital before they go home, often they'll get a hepatitis B vaccine. Tell us a little bit about hepatitis B, the disease, and why we would want to vaccinate against that. And then, why do we start at birth?

Dr. Michael Brady: So hepatitis B, it's an infection that primarily impacts the liver. So the virus goes to the liver. It actually can go to some other places, but the major damage is the liver. And probably somewhere in the neighborhood of 5% to as high as 90% in young babies will go on to develop chronic liver infection, which could then lead to chronic liver disease, cirrhosis and even cancer of the liver. So, that obviously is something that is very serious and hepatitis B vaccine was our first cancer vaccine. 

The reason that we start giving it at birth is that, as I mentioned, children who are born to mothers who are infected with hepatitis B, if they become infected, there have about a 90% chance of going on to developing chronic liver disease and then progressing to cirrhosis and to cancer. Most people may not have known this, but before the hepatitis B vaccine, 25% of all the people in the United States with chronic hepatitis B liver disease were actually children who had acquired their infection from their mother.


So, one of the things that we want to do is make sure that we get the protection very early because that's the time period where there's the greatest risk for the infection resulting in chronic disease. And, we actually did experience that 25% of all individuals with chronic hepatitis B infection were actually infected as children. 

Dr. Mike Patrick: And it's not just a one-time vaccine at birth. Kids then also get this at two months and around six months?

Dr. Michael Brady: Yes. The hepatitis B vaccine needs kind of like a prime and then a boosting in order to get the best immune response to protect the baby. And so, we do get three doses. Fortunately, it may be included in some of the combination vaccines which makes it easier to administer without having to give extra shots. So that's always a good thing. 

Dr. Mike Patrick: The next vaccine that folks will usually come across then is at the two-month visit. And they'll get that second hepatitis B vaccine and  then also DTaP. Tell us about that vaccine. 

Dr. Michael Brady: Okay. So, the DTaP right now contains vaccines against diphtheria, tetanus and pertussis. Now, diphtheria which was a significant problem back in the 19th century has been pretty much wiped out in the United States because of the vaccine. And there are still countries around the world where diphtheria occurs. And we were kind of recognizing now with things like Zika and other things that we do really live in a global world, that it is important to maintain immunity for that. But most people in the United States would have never ever seen a patient would diphtheria. 


The second one is tetanus. Again, tetanus is something that can be very, very serious. And one other thing is even though we don't see tetanus because of the immunizations, the organism is still in the ground, which is kind of where we acquire it. It is get a cut and it gets contaminated. And so, our risk right now for getting tetanus is just as great as it was before the vaccine if we don't get immunized.

And so, there's really no opportunity for what we call herd protection or community protection for tetanus. So you really do need to get the tetanus vaccine. 

And then, the last one is pertussis which is kind of a little bit of a concern right now in that we'd actually had really good protection against pertussis when the vaccine first became available. It became available in late 1940s. And up in through most of the 1980s, the numbers of cases of pertussis report in the United States were very very low. And that was very good. 

Unfortunately, there were some issues concerning the pertussis vaccine we're doing at the time. It was known as a wholesale pertussis vaccine, where they just took the entire bacteria, and as you mentioned, they used formalin to kill it, and then used that as the antigen in the vaccine. It definitely caused of number of local reactions, so it was unusual for somebody to maybe get a large red area where the shot was. Or, even sometimes the whole arm would get red, cause some children to get fevers, to become irritable. 

So, it did have some consequences that were concerning. The biggest one that created the problem and the reason we had a change to an acellular vaccine actually was related to a concern about the vaccine adverse event that actually turn out not to be true. So if you look in the Red Book, back until the late 1980s, you will see that there was a concern about the possibility of a child getting encephalopathy after receiving the whole cell pertussis vaccine. And the risk was dated to be 1 in 300,000 doses. 


That was based on a study that was done in Great Britain in the 1960s. And at that time, analytic capabilities were not quite as good as they had become. And it was determined in the early 1990s that actually the analysis was flawed and there really wasn't any increased risk of getting encephalopathy with the pertussis vaccine compared to not getting the pertussis vaccine. And that happened, the information became available at about the same time that the vaccine for pertussis got changed from the whole cell to the acellular pertussis vaccine. So, fortunately, we rarely now see the reactions to the pertussis vaccine with the redness, swelling in the arms, high fever, et cetera. 

Dr. Mike Patrick: Which sometimes would cause serious but that was a febrile seizure, which is not particularly dangerous. 

Dr. Michael Brady: Right, yes. But we kind of accepted a vaccine that wasn't quite as successful as the whole cell pertussis vaccine. So since the early 1990s, we have continued to see additional cases of pertussis. And the major reason that we do is that the vaccine actually works very well but for a short period of time. So when we give it to young babies, they are protected. And that's important because pertussis is most harmful to young babies. So making sure that the infants are immunized in the first few months of life is essential, because that's where we're going to see pertussis hospitalizations and even many deaths. 


But the immunity to the vaccine will then wane over a few years. And that's why because teenagers were starting to become kind of a second group, there is now a recommendation for kind of an early adolescent Tdap immunization to try to see if we could reduce the number of people who are kind of spreading the pertussis, particularly the younger children. 

Dr. Mike Patrick: So the DTaP, the acellular one, DTaP, we give it two months, four months, six months and then another booster around 15-18 months of age. And then, they get another one before they go to kindergarten. 

Dr. Michael Brady: That's right, yeah. 

Dr. Mike Patrick: Four to six years of age. And then, a slightly different version of that vaccine, the Tdap that you had mentioned is given then when kids are 10 to 12 years old, somewhere around that age range. And then, also to pregnant women as well because we want to really to be sure to protect their baby when it's born, that there's no one to give the kid pertussis. 

Dr. Michael Brady: Right. So, yeah, one of the things that I think we're going to start to seeing more is maternal immunization to protect infants. So Tdap is one where if the mom receives it probably somewhere around the middle of the pregnancy, the mom will develop antibodies. 

And again, the vaccine does work. It's the duration of antibodies out there. So the mom will get nice levels of antibody. And fortunately, mothers are very giving. They give their babies the antibodies across the placenta. And then, the babies are born with antibodies against pertussis. And that's really valuable because as you mentioned the first dose is given at two months of age. And so this will give us an opportunity to have some protection for the first few months of life. 


Dr. Mike Patrick: One interesting thing, the diphtheria portion of this vaccine and the tetanus portion, we're not really protecting against the bacteria but against the toxin that these bacteria produce, correct? 

Dr. Michael Brady: That's correct, yes. So very, very small amounts of the toxin released from each of the two different bacteria are what caused the disease. And so, we aren't trying to prevent infection. What we're trying to do is prevent the disease that's caused by the release of the toxin. The components of the vaccine are what are called toxoids, which means that they are toxins that have been modified so that they no longer cause disease. But they are still are capable of causing an immune response that will protect you from the toxin. 

Dr. Mike Patrick: Which is what causes the disease. 

Dr. Michael Brady: Right.

Dr. Mike Patrick: So not the bacteria itself. Very interesting. 

Let's move on. Another one that kids get basically along with DTaP, the Hib vaccine, which protect against Haemophilus influenzae type b . And kids get this again at two months, four months, and then some at six months depending on the specific vaccine, and then again at 12 to 15 months of age. And I should mention, so it's Haemophilus influenzae type b, but this is not the flu which is a virus. This is a bacteria. Why do we want to protect against that particular disease? 

Dr. Michael Brady: So this is one of the vaccines that kind of occur during my career that I'm most excited about. Haemophilus influenzae type b causes invasive disease. One of the most serious consequences is meningitis. But it also has some other consequences, a condition called epiglottitis where you have a very very difficult time breathing and sometimes can lead to death. And then, it causes a number of other less serious but invasive complications. 


To give you an example, before this vaccine was available at Nationwide Children's Hospital, we would have about a 120 children hospitalized with invasive Haemophilus influenzae type b and 60 of those children will have meningitis. And, somewhere in the range of about 5% to 10% would die. And maybe up to as high as half of them would end up with some type of long-term complications, the most common would be hearing deficit, but other kind of intellectual and other problems were also occurring. 

And when we got the conjugate Haemophilus influenzae type b vaccine, we can usually count over a decade on one hand the number of kids that we see with invasive Haemophilus influenzae type b diseases. It's really gratifying to not have to see a patient who has this particular condition and talk with the families about what the potential outcomes are going to be, and just hope that we've started medicine early enough that we can actually change the outcome. So it is an extremely valuable addition to our vaccine armamentarium. 

Dr. Mike Patrick: It really has changed the practice of pediatrics in terms of young kids who have the high fever. Where prior to 1990, a lot of those kids got admitted because you wanted to make sure you it wasn't this or get the treatment started right away. And now, a lot of kids with high fevers, we know it's a virus and don't really think twice about it. So big difference. 

Dr. Michael Brady: Right. So the combination of the Haemophilus influenzae type b vaccine and you'll probably going to ask me about the pneumococcal conjugate vaccine… 

Dr. Mike Patrick: Yes. 


Dr. Michael Brady: Both of those have kind of also changed how the pediatrician think when the child has a fever. You mentioned about hospitalization, but even a larger proportion would probably have gotten a spinal tap based on the fact that, again, people are concerned about the possibility of meningitis. So, it has definitely made the infection less common, but also kind of improved the ability to manage the children. 

Dr. Mike Patrick: So once the Haemophilus influenzae infections really decrease because of the immunization, then more percentage of invasive disease that kids were hospitalized for since there was a Haemophilus influenzae around to make them sick, became the pneumococcus or Strep pneumonia. So kind of spring boarding off the success of the Hib vaccine, then the pneumococcal vaccine for kids came to be. 

Dr. Michael Brady: Yes. So invasive pneumococcal disease was probably more common than invasive Haemophilus influenzae type b disease, but a lot of the invasive disease was pneumonia. But there also was meningitis and there were a number of other things mastoiditis, and even not necessarily that invasive but problematic — otitis media, ear infection, et cetera. 

So it did become very clear that you could develop a vaccine related to producing antibodies against the capsule or the bacteria which is important for protecting us from Haemophilus influenzae type b and the pneumococcus. So they did develop these vaccines and had to overcome the situation where very young children don't respond to the polysaccharides from the capsule very well unless you hook up protein to it. That's why we call them conjugate vaccines. So they're polysaccharides conjugated with a protein. 


We have had a dramatic decrease in invasive pneumococcal disease as a result of the conjugate pneumococcal vaccine. One of the things that's a little bit different with Haemophilus influenzae type b and pneumococcal is that there is really only one serotype that cause most of the  Haemophilus influenzae type b disease, whereas there is about 90 different serogroups of the pneumococcus and in the United States maybe as many as 30 or 40 caused invasive disease. 

So the first conjugate vaccine, the vaccine was made from the seven serogroups that caused the most disease. And when it came  out it made a dramatic decrease in the amount of invasive disease we're seeing due to the pneumococcus. But, as was probably anticipated, we started to see some increases in cases due to different strains that weren't included in the vaccine. So we went from a vaccine with 7 strains to now we have a vaccine with 13 strains. And so, we have kind of recovered and gotten rid of almost all the cases. And we anticipate that probably there'll be some strains that become increased in number because they're not in the vaccine but that really hasn't happened too much yet. 

Dr. Mike Patrick: And if it would, you would expect "Well, we'll try to add those strains to the vaccine in the future if we needed to." 

Dr. Michael Brady: The other thing that's really nice about this particular pneumococcal vaccine is well, a very large amount of the disease is seen in young children is actually seen throughout the entire lifespan. And by the introduction of this vaccine, one of the groups that seems to get most disease is the people over age 65. There was a dramatic decline in invasive pneumococcal disease with the serogroups in the vaccines that were seen in people over 65, and actually between the ages of 20 and 65. 


So when you were talking about herd immunity or community protection, what happens is these vaccines not only protect you against getting disease, but it also protects you from actually carrying the bacteria in your nose. And so, when the grandparents pick up this young baby who's been immunized, they aren't going to get exposed to the pneumococcus and that has resulted in significant improvement and health not only of children but also of grandparents. 

Dr. Mike Patrick: Yeah, very interesting. And pneumococcal vaccine is given also 2 months, 4 months, 6 months and then the booster, 12 to 15 months of age, much like the Haemophilus influenzae vaccine. 

Polio, so kids get a polio shot these days. When I had my polio shot, it was actually oral. And actually my daughter, hers was oral as well. Why did we switch from oral polio vaccine to a shot? 

Dr. Michael Brady: So the original vaccine for polio was actually the shot. As was kind of mentioned before, sometimes what we would do is take a live organism and kill it and try to make it so it would be safe to go. And it actually worked very very well, but it was kind of identified that if you gave a live — what's known as attenuated or a vaccine that has been changed and modified so that it doesn't cause the disease — that you could do a couple of different things. 

So one, you could immunize the person and they would get immunity in their intestinal tract which is where the polio virus multiplies. And so, you could then get protection of the individual who received the vaccine. But also if the person got the vaccine and they got exposed to polio, it wouldn't multiply in their intestinal tract and they wouldn't spit it to other people.


Now, another consequence which is questionable whether or not this is something you would push is the fact that it also allowed… Because when you give it to young children, they have a tendency to share things, and one of the things that they frequently share are gastrointestinal organisms, that we sometimes immunize children who aren't immunized because they would end up getting exposed. So it was seen as a really, really good way to try to get the polio vaccine out to a large number of people, protect shedding from people who may be asymptomatic because they got their vaccine to other people and maybe even get a little bit of herd protection in a slightly different way. 

Well, the one problem with this particular vaccine is the fact that every once in a while when viruses kind of multiply, they make mistakes. And if they happen to make a mistake that illuminates the change that had occurred to make it a safe vaccine, it may actually revert to a virus that can cause polio. 

And so, if you kind of look at the risk of getting polio in the United States since in the late 1980s, we said there was no more endemic polio in the Western hemisphere. It was really pretty low-risk. Even though, again, you could get it from people coming from other countries. You could travel to other countries and they still have polio.

There was a decision made that we needed to kind of look at the fact that we did have a vaccine that was very effective. And we have a low risk, and there is a slight risk actually in the United States. We would have between one in six cases of vaccine-associated polio each year despite the fact that there were millions and millions of doses. I was a small number, but it was still not zero. And we can go to zero if we gave the shot. 


So, it was a decision in the United States to go to the shot. Now, around the world, most of the non-industrialized nations still use the oral vaccine. One, it's easier to distribute since you don't need to use needles. It also is about 95% less expensive. So there's some advantages. But, the World Health Organization is actually kind of working on a number of different approaches to try to get to getting rid of the oral vaccine in the next few years. 

Dr. Mike Patrick: So this one example of the surveillance system in action and working where you saw this association with the vaccine and actual polio disease, although very rare but you still noticed it, saw it, and reacted to it by then switching the vaccine to make things safer. And I think that's important reassurance that the system in place — to watch for these things and react to them as they occur — works. 

And then, the other oral vaccine, which is still an oral vaccine is rotavirus. Tell us a little bit about that vaccine. 

Dr. Michael Brady: So rotavirus is a very common infection. Up until the rotavirus vaccine, it was the most common cause of diarrhea in young children. And anybody who's had a child in child care would kind of attest to the fact that rotavirus kind of runs through different areas very quickly. 

So the current rotavirus vaccines are live attenuated vaccines. And there's two of them and they both had been shown to be very safe and very effective. But, actually, the first rotavirus vaccine that we had was also a live attenuated vaccine that was given in the late 1990s. 


And as you mentioned, because of the monitoring system, it was noticed that the infant who received the rotavirus vaccine at that time had a higher risk of developing a condition called intussusception. That's where part of the intestinal tract kind of moves its way into the kind of a…

Dr. Mike Patrick: Kind of telescoping in itself. 

Dr. Michael Brady: Right. And it can cause some blockage. And so, the vaccine was pulled off the market. And the companies decided they needed to try to work on a different way to attenuate the virus so that it wouldn't cause this. 

So the vaccines had been available now for almost a decade. And right now, rotavirus disease in the United States is very rare. Again, this was an interesting situation where you give the rotavirus vaccine to young infants that there has been dramatic decrease in rotavirus disease in all age groups. And so, that's been very, very valuable. 

Dr. Mike Patrick: And again, that community protection idea. 

Dr. Michael Brady: Right.

Dr. Mike Patrick: It ended up being, even with the intussusception, with that first rotavirus vaccine, it was just about 1 in 12,000 infants had that potential. And still it got picked up, it's taken off of the market, and there was reaction to the fact that this was happening. So another example of that warning system in place. 

Dr. Michael Brady: Well, so obviously, because of that original concern, there was going to be very, very good monitoring of the two new vaccines. It's kind of interesting they actually did identify that following the immunization with either of those two vaccines, that there did appear to be a slight increased risk of intussusception associated with both of those vaccines. It was ten times less likely than with the RotaShield, which was the original vaccine. 


What's kind of interesting is they've looked at intussusception rates in the United States since the introduction of the two vaccines, and it's actually gone down a little bit. And so one of the kind of situations that I think explains this is rotavirus is probably one of the initiating factors for intussusception in young infants. And so, it may not be that hard to understand why a live attenuated vaccine may slightly increase your risk for intussusception since probably the real disease significantly increases your risk. So by reducing rotavirus diseases, we are now significantly protecting the infant from not only having diarrhea but probably also for intussusception. 

Dr. Mike Patrick: Yeah, very interesting. Well, we appreciate you stopping by. We're going to cut things off for this week. But as I mentioned in the introduction to this program, we have a lot to cover. So we're going to stop now, but then we'll get back to this and continue going through all the childhood vaccines next week.

I want to remind folks in the Show Notes for, there's some links for you. I talked in the intro about "The Vaccine War" which was a PediaCast interview where I interviewed Seth Mnookin who's the author of  The Panic Virus: The True Story Behind the Vaccine-Autism Controversy. So, we haven't mentioned that at all in this program, but it's because we've done so much of that in the past and had that entire episode, 329, dedicated to that story. So we'll put a link in the Show Notes so you can find that easily. And then, also a link to the recommended immunization schedule the most up-to-date one from the Centers for the Disease Control, we'll have a link to that as well. 


Part 2 is coming next week. We're going to talk about the flu — so influenza, the virus version, not the bacteria Haemophilus influenzae — MMR (measles-mumps-rubella), Varivax (which protects against the chicken pox virus), hepatitis A, the meningococcal vaccine and the HPV vaccine as well. 

We'll also answer the questions next week — are all these diseases really still dangerous with modern medicine? Could it be that we could actually just treat these diseases rather than have to prevent them given improvements and improved supportive care? That's an argument that sometimes is out there as we compare modern medicine to the pre-vaccine era. 

Are we given too many shots? Can kids handle so many injections at one time? Again, questions that come up, so we want to address them.  

And what about alternative vaccine schedules? Do they add any benefit? Could they pose other problems? So be sure to join us next time as we continue our journey through the world of childhood immunizations? 

Dr. Michael Brady has been our guest, pediatric Infectious disease specialist here at Nationwide Children's Hospital, thanks for stopping by today. 

Dr. Michael Brady: Thanks for having me. I appreciate the opportunity. 


Dr. Mike Patrick: All right, we are back with just enough time to say thanks to all of you for taking time out of your day to make PediaCast a part of it. Really do appreciate that.


Also, thanks to Dr. Michael Brady, Pediatric Infectious disease specialist here at Nationwide Children's Hospital.

That's all the time we have today, but again we're going to continue this conversation next week and have a part two of childhood immunizations, childhood vaccines, as we cover more of the shots that kids get these days. 

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Thanks again for stopping by, and until next time, this is Dr. Mike, saying stay safe, stay healthy, and stay involved with your kids. So long, everybody. 


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