The vaccine timeline for young kids is looking a little more solid. This morning, Pfizer submitted data to the FDA showing that its COVID-19 vaccine is effective and safe for children ages 5 to 11. And this afternoon, the company’s CEO, Albert Bourla, said that trial results for even younger kids, aged 2 to 4, will be available in a couple months’ time. “Before the end of the year,” he confirmed in an interview with Craig Melvin, the Today news anchor and MSNBC anchor, at The Atlantic Festival. Submission to the FDA will follow soon thereafter, Bourla said.
The wait for COVID-19 vaccines comes during an ongoing surge of cases among children. Vaccines are taking this long to reach kids because the trials follow the classic strategy of age de-escalation. Manufacturers first tested their shots in adults, then teens, and most recently kids as young as 2. Pfizer is also running a pediatric trial for the youngest children, aged six months up to 2 years old. Bourla did not specify a timeline for this cohort, but expect results sometime after those from the 2-to-4-year-old group.
Once the results for each age cohort are collected, Pfizer will submit them to the FDA to review for safety and efficacy. The agency doesn’t work on a set timeline, but for context, emergency use of Pfizer’s vaccine took 21 days from filing to authorization for adults and 31 days for teens age 12 to 15. If that precedence holds, then kids 5 to 11 will likely be able to get shots around Halloween and those 2 to 4 will be eligible by early next year. (Don’t be surprised if those timelines stretch, however.)
All eyes are on Pfizer’s vaccine because its pediatric trials are furthest along. Moderna and Johnson & Johnson, the two other companies whose COVID-19 vaccines have been authorized in the United States, haven’t yet released any data from their trials running in children under 12. (Like Pfizer’s trial, these also go down to children as young as six months.) The first shot available to kids will almost certainly come from Pfizer.
The adult and pediatric trials of COVID-19 vaccines do differ in a couple of key ways. First of all, Pfizer is testing a smaller dose in kids. For adults and teens, each shot of Pfizer’s two-dose regimen contained a 30-microgram dose. For kids 11 and under, the dose was reduced to only 10 micrograms a shot, and then reduced even further to 3 micrograms for kids six months up to 2 years of age. Based on Pfizer’s announcements, the data the company has collected so far suggest that the smaller dose is indeed safe and coaxes a strong immune response out of the 5-to-11-year-old cohort; their antibody responses are similar to that of adults who got the higher dose.
Speaking of that immune response, scientists are evaluating the vaccine’s efficacy in kids somewhat indirectly—this is another way these adult and kid trials differ. The COVID-19 vaccine is already known to be effective in adults, so researchers are looking at antibody responses rather than counting the number of vaccinated versus unvaccinated people who get COVID-19, as they did in the original adult trial. Studying efficacy by waiting for enough kids in a trial to get COVID-19 would require a much larger trial—and much more time to complete it. These trials that focus on antibody response are called “immunobridging” studies and are standard in studying vaccines.
Even when young kids are able to be vaccinated, however—and polls right now suggest that many parents are still hesitant—the coronavirus is unlikely to go away. This is why pharmaceutical companies including Merck, Roche, and Pfizer are also racing to develop antivirals to treat patients with COVID-19. This week, Pfizer announced that it is studying an oral pill that could block the replication of the coronavirus. Trials are “ongoing right now” to see whether the pill can mitigate or prevent COVID-19, Bourla told Melvin, and the first results are expected before the end of the year. The world is heading into a third year with the coronavirus, but this time with many more pharmaceutical defenses in the arsenal.