Big news! Yesterday Pfizer-BioNTech announced that they have completed a Phase I trial to determine the best dose for their COVID-19 vaccine in younger kids, and they’re moving on to Phase 2/3 trials which will test effectiveness and safety in children ages 6 months to 11 years.
The short version: the Phase 2/3 trial green light says that there were no serious safety issues identified in this first trial in kids. Based on the results, Pfizer-BioNTech is going forward with testing lower doses in younger age groups. In a press release, they said they expect to submit Phase 2/3 trial results to the FDA in September or October. At that point, we will have information about safety, effectiveness in terms of immune response, and side effects for the Pfizer-BioNTech vaccine in kids ages 6 months to 11 years. Vaccines for younger kids will NOT be available in the US in time for back-to-school next year but may become available before the end of 2021.
In a small (Phase I) study of a little more than 100 kids, they found that lower vaccine doses produced the best balance of immune response and tolerable side effects. They did not release the results of this trial, so we don’t know what the side effect rates looked like at the various doses they tested.
The doses they are taking forward into the next testing phase are smaller than the adult & adolescent dose. Kids ages 5-11 will get a 10 microgram dose, and kids ages 6 months through 4 will get a 3 microgram dose. This is smaller than the 30 micrograms that was authorized by the FDA and WHO for use in everyone ages 12+. Each child will still receive 2 doses, spaced 3 weeks apart.
Pfizer-BioNTech will now start enrolling about 4,500 kids ages 5-11 in a Phase 2/3 trial. Trial sites are in the US, Finland, Poland, and Spain. In these trials, there will be 2 kids who get the vaccine dose for every 1 kid who gets assigned to the placebo group. Kids participating in the trial will get two 10 microgram doses, spaced 3 weeks apart.
Pfizer-BioNTech said that they expect to also start a Phase 2/3 trial for kids ages 6 months through 4 years in the next few weeks. In this trial, participants will get 2 doses that are 3 micrograms, spaced 3 weeks apart.
The science team will be looking for an immune response in these trials, NOT a comparison of COVID-19 cases between the placebo and test groups. The reasons for this include 1️⃣ cases are way down in the study locations, so it would take a very long time for the trials to accumulate enough cases to make conclusions. We don’t want to wait years–we want results as soon as possible. And 2️⃣ previous trials have already established that an immune response is causally linked to preventing infections, so we don’t need to establish that again here.
Pfizer said they will have results and request Emergency Use Authorization from the FDA in September or October.
After that, FDA will call an emergency meeting of their independent panel of experts to review the safety and efficacy data from the trial. They will review the data and meet within days to weeks of Pfizer’s request. They will likely look at ages 5-11 first and then the younger group. There might be a gap between decisions for the different age groups, with a decision for 5- to 11-year-olds coming first.
The independent expert panel and FDA will make a decision about whether to authorize the vaccine at these doses based on the trial data. The FDA panel makes their decision based on whether the benefits of the vaccine (mostly preventing COVID-19) outweigh any risks of the vaccine that showed up in the trial.
If they decide the benefits outweigh the risks, they will authorize it, and then it will go to a second decision with CDC’s independent panel of experts. They will make a similar calculation before recommending the vaccine to kids. At that point, it will go to the various State panels, who decide to expand the eligibility criteria accordingly. All this will take at least a couple of weeks from when Pfizer-BioNTech submits the trial results to FDA.
So we expect to have more information in September or October. Vaccines for younger kids will not be available in time for back-to-school 2021, but–if these trials demonstrate that the benefits outweigh the risks–they may be available before 2021 is out.