Pediatricians Discuss Children’s Vaccines, the Immune System & Autoimmunity

Pediatricians discuss children’s vaccines, the immune system & autoimmunity

Zachary Rubin, MD: Hi, I'm Dr. Zachary Rubin. I'm a pediatric allergist and clinical immunologist practicing just outside of Chicago, Illinois.

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 Perelman School of Medicine at the University of Pennsylvania.

Zachary Rubin, MD: Do vaccines have long-term side effects?

Paul Offit, MD: So, if by long term you mean side effects that don't show up within a few weeks, but show up one year, two years, five years, 10 years later, no. Vaccines can have serious side effects, including side effects that can cause permanent harm, side effects that can cause a child to die. I mean, that is true, and I'll give you some specific examples.

The oral polio vaccine, for example, was a rare cause of polio. It occurred in roughly 1 per 2.4 million doses. It was rare, but it was real. The yellow fever vaccine is a rare cause of something that has a fancy name of viscerotropic disease, which is a nice way of saying yellow fever. It happens in about 1 in a million people, primarily over 65, but it was real. Measles-containing vaccine can cause a lowering of the platelet count, which are cells in your body necessary for clotting. It happens in about 1 in 30,000 people, again, rare but real. But all those severe events when they happen, happen within six weeks of a dose. I mean, for the 200 years of vaccine development, starting back in the smallpox vaccine, I can think of no example really where a vaccine was found to cause a side effect that wasn't determined for years because it didn't show up years later.

Now, sometimes something is so rare like polio caused by the oral polio vaccine that you're not going to see it in a study of a thousand or ten thousand or even a hundred thousand children. You're only going to see it when it's in hundreds of millions of children, which is the way that that was picked up. But in terms of long-term side effects, no.

Zachary Rubin, MD: Yeah, I agree. In terms of what I tell families, the immune response is done within four to six weeks of vaccination, and the adverse events that occur happen due to the body's own immune response creating those side effects itself. It's not necessarily the foreign substance that is the problem, it's how our immune system responds to it. So, as you said, it's going to take millions of doses to find these rare, potentially serious adverse events that occur, which we're not going to necessarily pick up on pediatric trials right away.

Do vaccines increase the risk of autoimmune disease?

Paul Offit, MD: Vaccines are an extremely rare cause of autoimmune disease. So, by autoimmune disease we mean that if you're given a vaccine, like say the influenza vaccine, your body will make an immune response to the proteins that make up influenza virus. But sometimes, inadvertently, there's cross-reactivity, if you will, between a protein on a virus and a protein on the surface of your own cells.

So, for example, with the influenza vaccine, rarely, you can see that not only do you make an immune response to the vaccine, but you also make an immune response to one of the proteins that line the sheaths of nerves called myelin basic protein. The side effect can be something called Guillain-Barré syndrome, which is a rare neurological disorder that's characterized by this sort of ascending paralysis, and it can be a serious phenomenon. It occasionally happens with the influenza vaccine as frequently as 1 per million doses. So, it's extremely rare, but it does happen.

So, you would ask the reasonable question, the logical question, if that's true, if the vaccine causes it, causes you to make an immune response not only to the vaccine virus proteins but also to proteins on the surface of your own cells, wouldn't the natural infection do the same thing? And the answer is, yes. And, if you look at people who are infected with influenza virus, about 17 of every million people infected will develop Guillain-Barré syndrome. So, you're actually 17 times more likely to have this autoimmune response when you're naturally infected than when you're vaccinated. You could make the argument, actually, that the vaccine protects you against Guillain-Barré syndrome because it protects you from being naturally infected.

Zachary Rubin, MD: Are vaccine doses based on weight?

Paul Offit, MD: Vaccines are not like an antibiotic, for example. I mean, if you take an antibiotic like amoxicillin, what matters is the quantity of that drug in your bloodstream at a specific period of time. So, your size matters. The volume of blood in your bloodstream matters. That's not true with vaccines. With vaccines, you give it, for example, typically as a shot in the arm and then that vaccine is taken up, ultimately, by local draining lymph nodes and processed and presented to the immune system. So, size doesn't really matter. And often the dose of the vaccine or the quantity of a vaccine that's given to a child is similar, if not identical, to vaccines that are given to adults.

Size doesn't really matter, no.

Zachary Rubin, MD: Vaccines are age-based in terms of how the immune system matures. The one analogy I like to make for folks to understand is that when you have a new car, you don't need as much maintenance on it. And so, the vaccines have lower doses because a younger immune system is more robust. It's going to be able to generate antibodies much more easily with a smaller amount. But as you get older, you're going to need more antigen, more of a dose to create that immune response. Just like with cars, you may need more maintenance, more work on it to keep it going.