Coadministration of Vaccines for Children Younger Than 5 Years


Expert pediatricians discuss challenges with coadministration of vaccines in children younger than 5 years.

William J. Muller, MD, PhD: One of the discussion points at the VRBPAC [Vaccines and Related Biological Products Advisory Committee] meeting was coadministration of vaccines, especially for young children who are getting their primary vaccine series for other diseases. Do you have any thoughts about what to tell parents about that?

Paul A. Offit, MD: Typically, when a vaccine is put onto the schedule, there are concomitant use studies. You have to prove that your vaccine doesn’t interfere with the safety or immunogenicity profile of the vaccines given at the same time. Conversely, that those vaccines don’t interfere with the safety or immunogenicity profile of your vaccine. Those studies haven’t been done for vaccines that are going to be given to children younger than 5 years. The way companies did those studies is they never gave those vaccines at the same time, so you have no information about giving those vaccines at the same time. The American Academy of Pediatrics said in the past 24 hours that when these vaccines roll out, pediatricians could give them at the same time. Personally, I would take a more cautious approach.

The Moderna vaccine had an incidence of fever in the 25% range, and for those with temperatures of 38-39 °C, that was about 18%. For those with temperatures of 39-40 °C, that was about 4% of those children, and for those with temperatures greater than 40 °C, it was 0.4% of the children. And fevers are an issue for younger children. I would prefer, until we get more information, to have a 2-week separation, which is going to be very difficult for pediatricians. Because for a 6-month-old child, if you wanted to start they really should be 6 ½ months of age, and then you need to boost 3 or 4 weeks later, depending on the vaccine. That’s not going to make life easier for the pediatrician. I think what the American Academy of Pediatrics is trying to do is make life easier for the pediatrician by saying you can use it concomitantly. Although I was fortunate enough to be part of a team at Children’s Hospital of Philadelphia in Pennsylvania that created the rotavirus vaccine, concomitant use studies are bare. You have to show you don’t interfere with the immunogenicity profile of existing vaccines, which means you’re doing a lot of testing looking at immune responses. It’s a lot of work that wasn’t done here because it’s a pandemic, and you want to get the vaccine out there. But I would take a more cautious approach until there’s more data.

William J. Muller, MD, PhD: And in defense of study design, as we’re generating data on adverse effects of new vaccines, we don’t want to confound that data with existing vaccines, which we already know can promote some adverse effects we’re seeing with the COVID-19 vaccine. I think that’s a concern when you’re trying to design the initial studies, but down the road, we’re going to have to get more data to understand exactly how these vaccines interact with each other. I was a little surprised when the Pfizer vaccine was authorized in older children, and CHIP said to give it without regard to other vaccinations, even though it hadn’t been studied that way.

Paul A. Offit, MD: I was surprised as well.

Transcript Edited for Clarity

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