Here are the top three questions that the FDA panel of experts considered during their meeting:
The committee focused primarily on evaluating the safety of vaccines for children and the potential gains in protection for children and society as a whole if they are ultimately used for younger Americans.
A big consideration for regulators: Children’s developing immune systems appear to respond to Covid-19 differently than adults. Children are generally less likely to develop severe Covid-19 than adults – but a small percentage develop a severe inflammatory syndrome called MIS-C that adults do not have.
More than 300 children in the United States have been hospitalized with the disease, and recent data from the Centers for Disease Control and Prevention shows that hospitalizations are on the increase. Children under 5 and teens have higher hospitalization rates than children 5 to 11, according to federal data.
“We’re going to have to have a highly vaccinated or highly immune population for years, if not decades, and it just seems silly to think that we’re not going to have to include children in that framework,” said Paul Offit, pediatrician at Children’s Hospital of Philadelphia.
Others were more careful. Cody Meissner, professor of pediatrics at Tufts University School of Medicine, said children need a safe and effective Covid vaccine – but opposed allowing emergency use in anyone under the age of 18, saying currently available safety data is insufficient.
“The burden of disease is so low and the risks are just not clear,” he said.
And while clinical trials are designed to detect common side effects, some rarer conditions related to vaccination may not appear until after an injection is widely used. Federal health agencies are now examining reports of heart inflammation in some people under the age of 30 who have received mRNA vaccines from Moderna and Pfizer.
Although the conditions are rare, the CDC has found more cases occurring after the second injection of an mRNA vaccine, with early data showing around 16 cases per million second doses.
The panel wondered whether it was more important to test a large cohort of children or to monitor their immune response over a long period of time. “We don’t see more adverse events later,” said Hayley Gans, a pediatrician at Stanford University, of the Covid vaccine trials. Instead, she sees larger studies over a shorter period of time to rule out even the rarest adverse events, like heart inflammation.
Other committee members acknowledged uncertainty over how Covid might spread once fall and winter arrive, and people across much of the country are starting to spend more time indoors. . Experts on the panel expressed concern that they would not have a vaccination option for younger populations by then. Several pointed out that children are still vaccinated against rare or non-existent diseases in the country, such as measles and polio.
The effectiveness of the vaccine is normally calculated in clinical trials by comparing the number of infections in study participants who received the vaccine to those who received a placebo. Tests are designed so that data is analyzed at predetermined points; they can be stopped if the number of cases does not indicate any benefit from an injection, or continued to determine more precisely the effectiveness of a vaccine.
But because children are less prone to symptomatic Covid-19 infection than adults, it could take significantly longer for a pediatric vaccine trial to meet the statistical bar set by the FDA for vaccine studies for adults.
FDA officials are considering other approaches to measuring vaccine effectiveness, including studies that monitor the types of antibodies that vaccine recipients develop. If children who are vaccinated against Covid develop the same amount of protective antibodies as adults – especially if adults are as highly protected against the disease as they have been in clinical trials of the Covid vaccine, that real-world data has so far confirmed – scientists may consider the vaccine to be effective.
Measuring the level of antibodies in children who receive a vaccine is a well-established approach to demonstrating efficacy in the pediatric age group, said Doran Fink, pediatrician and deputy director of the Center for Biologics Evaluation and Research. If these antibody concentrations are comparable or higher than those measured in adults, researchers consider the vaccine effective in children.
How Covid Vaccines Mix With Routine Injections in Children
People receive most of their vaccines during childhood, often receiving more than one injection at the same time. The FDA has asked its advisory committee to consider whether children can be vaccinated against Covid in addition to routine childhood vaccinations.
The CDC recently updated its vaccine guidelines for adolescents and adults to approve the administration of the Covid vaccine alongside other injections. The agency did so in part because its data shows many teens are now behind on routine injections after more than a year of pandemic restrictions, with orders for tetanus-diphtheria-pertussis vaccines and human papillomavirus down about 18% from 2019.
Of minor concern is whether co-administered vaccines might interact with each other in a way that results in more serious side effects or reduced effectiveness. “We have to see if there is interference, not just with security… and with the immune response,” Gans said.