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Independent advisers for the US Food and Drug Administration (FDA) on Tuesday recommended the Pfizer-BioNTech Covid vaccine for children aged five to 11 – the first vaccine available for younger children in the US.
Of 18 members, 17 voted yes and one abstained.
Vaccines for children have been seen as crucial for protecting kids from the virus as well as slowing its spread, in addition to reducing the social and educational effects of school closing and attendance – and related economic concerns, such as caregivers’ ability to work.
The advisers weighed the vaccine’s effectiveness, the social and physical effects of the pandemic, and the potential risk of rare side-effects like myocarditis, a type of heart inflammation.
Data from Pfizer-BioNTech indicate the vaccine is 90.7% effective at preventing symptomatic illness among this age group.
The benefits of vaccination “clearly outweigh” the risks of myocarditis and pericarditis, FDA scientists concluded in an analysis, an assessment the independent advisers agreed with.
Making these decisions can be difficult and nerve-racking, but they are not made “when you know everything”, said Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia. “The question is when do you know enough.” In this case, he said, the benefits outweigh the risks, especially since myocarditis tends to be less common in pre-adolescent children.
“Our kids are going to be dealing with this virus for many years to come,” said Jay Portnoy, professor of pediatrics at the University of Missouri-Kansas City School of Medicine. “Getting the vaccine is just the first step that they’re going to take towards being able to protect themselves.”
Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research (CBER), highlighted the harms of the pandemic.
“Far from being spared from this harm of Covid-19, in the five-to-11 year-old age range, there have been over 1.9m infections, over 8,300 hospitalizations (about a third of which have required intensive care unit stays), and over 2,500 cases of multisystem inflammatory disorder from Covid-19,” Marks said.
Nearly 100 children in this age group have died, making it the eighth leading cause of death in the past year for this group. Children between five and 11 have one of the highest case rates of any age group, accounting for about one in 10 of all Covid cases in the country. They are also the most frequently affected by MIS-C, an inflammatory disorder that affects organs.
Children are “at least as likely” to be infected as adults, said Fiona Havers, medical officer at the CDC. But at the same time, cases among kids are more likely to go unnoticed, according to seroprevalence data indicating that about 43% of children have already been infected.
“There are many other adverse outcomes on children from the pandemic, including worsening emotional and mental health, decreased physical activity and loss of caregivers,” Havers said. “Lost in-person learning is another potential adverse outcome of Covid-19.”
The effects of the pandemic are unequal among children. Black, Hispanic and Native American children have a greater risk for developing MIS-C or dying from Covid-19.
Several advisers repeatedly pointed to the importance of vaccinating children in order to reduce cases throughout the country. While it is not yet clear how well the vaccine keeps children from transmitting the virus, data among vaccinated adults shows this is likely, and reducing the number of overall Covid cases through vaccination would help reduce spread.
“Children likely play an important role in transmission, and vaccinating children can help reach herd immunity,” said William Gruber, head of vaccination development at Pfizer.
The Pfizer-BioNTech trial included 1,518 children who received the vaccine beginning in June, as well as an additional 1,591 children who were vaccinated beginning in August, when the FDA asked the company to expand the trial in order to pick up on safety concerns.
Mild side-effects like fever and chills were less common among the kids than in older age groups. There were no reports of myocarditis among the approximately 3,100 children receiving the vaccine.
But serious rare side-effects like myocarditis may be “the principal concern people have regarding use of these mRNA vaccines and in children,” said H Cody Meissner, professor of pediatrics at Tufts University School of Medicine.
Myocarditis cases after vaccination tend to happen within a week, generally among adolescent males, and boys between the ages of 16 and 17 have the highest rate, at 0.007%, said Matthew Oster, a medical officer for the CDC. “Testosterone and hormones play a big role in this, which is part of why you may see a really high peak in adolescence and young adulthood, especially among males,” Oster said.
The FDA, in its scientific analysis, said the risks of Covid outweighed the risks of myocarditis. In one scenario that Hong Yang at the FDA called “purposefully conservative,” Covid cases could drop until more children are hospitalized from the vaccine than from the illness.
“If you just look at our track record in terms of predicting the epidemics, we’ve not done particularly well,” Pfizer’s Gruber said. “Given that the winter season is coming, the Delta [variant] is still up there, you still have a large number of susceptible children – there’s every reason to believe that the rate will not be at the nadir.”
Arnold Monto, acting chair of the committee, warned against “assuming that we are on the descending slope of the curve. Thinking that this is going to be the end of the wave permanently is maybe a little overly optimistic.”
While cases in the US have dropped since their recent height in September, coming cold weather and holidays may bring another spike.
The vaccine for this age group was formulated slightly differently, in order to extend its shelf life in a refrigerator from one month to 10 weeks, which should help the roll-out to pediatricians’ offices and elsewhere. The proposed dose for children is 10 micrograms, or one-third the adult dose of the Pfizer-BioNTech vaccine. The child-size doses look different from adult doses in order to prevent mix-ups, with caps and labels colored orange instead of purple.
Children 12 and up currently receive a higher dose than those 11 and younger. But antibody titers were similar across all age groups in this trial, potentially indicating that a lower dose could be sufficient for older children, Pfizer’s Gruber said.
On 2-3 November, advisers for the CDC will meet to discuss their recommendations as well. The FDA and the CDC will take the advisers’ recommendations into account when making the decision whether to authorize the vaccine.
While a little less than half of US children may already have some immunity after surviving Covid, it is not clear how well infection-acquired immunity will last, especially in the face of emerging variants. Reinfections are becoming more common across age groups, Havers said.