Watch Dr. Paul Offit, Director of the Vaccine Education Center, and Dr. Ripudaman Minhas, a developmental pediatrician, discuss common questions related to vaccines and development, including autism, vaccination during pregnancy, long-term risks, impact on the developing nervous system, and whether to delay pregnancy after vaccination.
Pediatricians discuss vaccines, pregnancy, development & autism
Ripudaman Minhas, MD: My name is Ripudaman Minhas. I'm a developmental pediatrician at St. Michael's Hospital, Unity health Toronto at the university of Toronto, and I see children with a range of neurodevelopmental conditions and inner-city trauma.
Paul Offit, MD: Hi, my name is Paul Offit. I am the Director of the Vaccine Education Center at the Children's Hospital of Philadelphia and a Professor of Pediatrics at the University of Pennsylvania School of Medicine.
Ripudaman Minhas, MD: So, from my background in developmental pediatrics, I've been getting a lot of questions around neurodevelopmental conditions, and particularly with autism. So, Dr. Offit, how would you approach that question when folks ask you about the link between vaccines and autism?
Paul Offit, MD: So, this notion was born in the late 1990s with a paper that was published in the Lancet, which is a well-respected general medical journal, by a British researcher named Andrew Wakefield, claiming that the measles, mumps, rubella, or MMR vaccine was associated with autism.
It was really, it wasn't a study. It was just a case series of 12 children, eight of whom developed autism within a month of receiving the vaccine. So, it raised the question. I mean, the nicest thing you could say about that particular paper, was it raised a question, could vaccines cause autism? And, certainly, you can see where parents are coming from. I mean, for some parents, child was fine, got a vaccine, now they noticed certain developmental issues or regression and wondered could this vaccine have done it. The good news, that's an answerable question. What you do is you look at thousands and now, frankly, hundreds of thousands of children retrospectively who either did or did not receive the MMR vaccine to see whether or not the incidence of autism was greater in a vaccinated group.
That study has been done 18 times, in seven different countries, on three different continents, costing, frankly, millions and millions of dollars, and the answer has been consistently the same, which is, the MMR vaccine did not cause autism, nor has any vaccine been shown to cause autism. But you know, it's hard to unring the bell. I think it's hard to unscare people once you've scared them. And once they have that notion in their mind that the vaccine might have done it, it's just hard to make that go away. Although, the good news is there was a study done by the Autism Science Foundation asking parents of children with autism, do you think the vaccine could have caused it? And 85% said no. So, that's good. That’s certainly not where we were 20 years ago.
Ripudaman Minhas, MD: When we think about all of our conversations now around vaccines for COVID-19, some of these questions are coming up again on with the idea that folks think of these as being new vaccines. And so, what are your thoughts on how, or what would you say around the idea of COVID-19 vaccines and how do we know that they won't have that sort of link. How would you approach that?
Paul Offit, MD: It is true that the approaches to making vaccines to prevent COVID are new approaches, the so-called messenger RNA approach, and the other one is the so-called vectored-virus vaccine approach with Johnson & Johnson. The mRNA approaches are with Pfizer and Moderna. Although those are novel approaches, they don't have a biology that is dramatically different from anything we've done before.
If you use the mRNA vaccines as an example, mRNA, messenger RNA, is just a small piece of genetic material that is then taken up into the cells, specifically in the cytoplasm of the cells, meaning not the nucleus where DNA resides, but in the cytoplasm where then that small piece of messenger RNA joins 200,000 other copies of messenger RNA, all dedicated to making the proteins and enzymes that keep us alive. In this case, the messenger RNA is going to make a different protein, which is the SARS-CoV-2 virus, which is the virus that causes COVID, the surface protein or spike protein, which it will do for a few days and then stop.
So, the process is really just a typical cellular process that occurs all the time. So, people can be reassured that there's nothing dramatically different really in the biology of these vaccines that is different from the biology of what occurs normally in people every day.
Ripudaman Minhas, MD: there's been a lot of conversation around vaccination during pregnancy as well. And so, when you think about long-term risks to the fetus and particularly from a neurodevelopmental disorder standpoint, what are your thoughts on that in vaccinating pregnant women?
Paul Offit, MD: Typically what happens is when companies do phase 3 trials, so-called large prospective placebo-controlled trials, often they don't involve pregnant women. That was true for say the two mRNA vaccines that came out in December, the Pfizer and Moderna vaccines. They should have. I really do think that those trials should've included pregnant women because pregnant women are at higher risk of suffering severe disease than women of the same age who aren't pregnant. So, it would have been nice to have had that information, but we didn't have it.
Now, typically what happens is the Centers for Disease Control and Prevention in this country, the CDC, will when there aren't clear data that were generated during phase 3 trials then say that the vaccine is contraindicated for use in pregnancy. They didn't do that here. What they did here was they said a pregnant woman could reasonably choose to get the vaccine. It wasn't a recommendation per se. It was just, you could reasonably choose to get it if you want, knowing that pregnant women were at higher risk of being hospitalized, going to the intensive care unit, being mechanically ventilated or dying as compared to women of the same age who aren’t pregnant.
So, thousands and then tens of thousands of pregnant women made that choice. When that happened, then the CDC was able, and published a paper with Tim Shimabukuro as the first author, to look at pregnant women who received the vaccine and compared them to pregnant women who didn't receive the vaccine to see if there were any differences in the outcomes of either the pregnancy itself or neonatal outcomes. And when they did that study, they found that there were no differences. The only difference is that pregnant women who chose to get the vaccine were now protected as were their newborns after the child was born, at least for six months or so. And with that, the CDC changed its recommendation to that the vaccine was recommended for use in pregnancy.
And then the CDC changed its recommendation again because they've noted a number of pregnant women who were being hospitalized, who were going to the ICU, who were delivering their baby severely prematurely. And so, they changed the recommendation to it's an urgent recommendation for pregnant women to get vaccinated.
Ripudaman Minhas, MD: Mums in my clinic also ask around, you know, if they were recently vaccinated, should they be considering delaying pregnancy if they're planning another pregnancy as well?
Paul Offit, MD: No, there's no reason to do that. As we said earlier, the mRNA technology for example, messenger RNA technology, is really a biological process that happens every day in your body. I mean, your body makes proteins. Your body makes insulin. Your body makes hemoglobin. Your body makes a variety of enzymes that help convert food into energy. This is no different. The only difference is you're making this viral surface protein for a few days. So, it's a natural process. I know it never feels like a natural process to be injected with a biological agent, but it actually uses just your cellular machinery to do what your cells are doing every day anyway.
Ripudaman Minhas, MD: There are a lot of questions that come up around the idea of what happens when a vaccine enters your body, and so folks seem to be concerned about the interaction of a vaccine with the nervous system or the developing nervous system. Do vaccines cross the blood-brain barrier?
Paul Offit, MD: So, the messenger RNA, for example, if we use the Pfizer or Moderna vaccine as example, will be taken up into the cell, make its protein for a few days, and then degrade. So, it doesn't really ever enter the blood-brain barrier, nor does the protein that it makes, nor do the antibodies that are directed against the protein.
So, the blood-brain barrier has the name “barrier” for a reason. It really excludes large proteins for the most part, unless there's another reason for why that blood-brain barrier has been disrupted, but the vaccines certainly won’t disrupt it.
Ripudaman Minhas, MD: And related to that, we wouldn't expect that there'd be accumulation like you’re saying because the mRNA does degrade as well. I know that’s been a concern in the past.
Thank you so much for answering these questions. I know that they've been on the minds of a lot of young families and folks that are planning to have families as well. So, thanks so much.
Paul Offit, MD: Thank you. It was my pleasure, and so nice to meet you.
Ripudaman Minhas, MD: Likewise.
Related Centers and Programs: Vaccine Education Center
Last Reviewed on Dec 23, 2021