Why Do Kids Need Their Own Vaccine Trials?

My younger child is two and a half, and he’s enrolled in the Pfizer COVID-19 vaccine trial. At this point, he’s had both doses (three weeks apart), but we don’t know if he got the vaccine or a placebo. In our trial, two-thirds of participants get the vaccine and the rest get a placebo injection that doesn’t contain the mRNA vaccine.

To be honest, I’m guessing placebo because of how minimal his physical reactions to the shots seemed to be, but it’s a bit tricky because he came down with hand, foot, and mouth disease about 24 hours after his first shot. Either way, we’ll know in about six months, which is when the clinical trial folks will reveal to us which injection he got, or when the US Food and Drug Administration issues an emergency use authorization for his age group, whichever comes first.

My husband and I had several talks leading up to the decision to enroll our baby—because although he’s two and a half, he still seems like a baby to me—in the trial. We said yes to the trial in the end because our general thought process was that it’s better to have a chance of him getting the vaccine than to let him go unprotected when the Delta variant is spreading rapidly throughout the United States.

Were we worried about how his body would react to the shot? Not particularly. We trust the doctors and researchers who’ve worked—in some cases around the clock—for months to create these life-preserving injections, as well as the physicians and scientists running our local trial. They spoke to us extensively before we enrolled in the trial about what it would involve, so that we could give our fully informed consent, and they reminded us that the trial is completely voluntary. We can opt out at any time.

More importantly, we trust the science that’s led us to this point. Millions of people have received the Pfizer COVID-19 vaccine since December, including my spouse and me, with very few side effects. Combined with the fact that vaccination is one of the best ways to not get COVID-19 and to minimize your chances of becoming severely ill if you do contract it, we felt grateful that there was a spot in the trial for him.

Plus, clinical trials for children are important, so we were glad that our healthy kid could, by participating, potentially help others. But why do kids need their own vaccine trials? Is it not enough that the vaccine has been extensively tested in adults? It turns out that just like vaccines should be tested in pregnant people, it’s important to test them in children too.

One reason is dosing. While the Pfizer COVID-19 is authorized for children as young as 12 years old, currently everyone receives the same dose. But young kids tend to have smaller bodies than adults, so finding the dose that will protect them adequately while causing the fewest side effects is essential. Just like in adults, the clinical trials for the COVID-19 vaccine in children started with a dosing study, in which volunteers received one of a range of doses. Once the dose that worked best for the most kids was established, then the research moved into the phase of the trial that my kiddo is in.

Another reason children need their own clinical trials is because they are still growing. Thus, their bodies work differently than those of adults in ways that can affect their development. A kid’s immune system is still so new that it may react to many immune challenges, such as those provided by a vaccine, differently than an adult’s immune system. Plus, it’s possible that receiving other childhood vaccines could somehow affect the COVID-19 vaccine’s effectiveness, so researchers need to keep an eye on that too.

Finally, children’s bodies change much more rapidly than adults’ bodies do, so it’s important to monitor those changes after something like a vaccine. Because I’m not growing much these days, it’s unlikely that my vaccine would have affected my growth and development, but that could be different for my two-and-a-half-year-old or for other kids his age. It’s a privilege to help researchers explore this and all of the other questions around the COVID-19 vaccine and kids.

Abby Olena
Dr. Abby Olena has a PhD in Biological Sciences from Vanderbilt University. She lives with her husband and children in North Carolina, where she writes about science and parenting, produces a conversational podcast, and teaches prenatal yoga.

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