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How safe COVID vaccines are for kids under 12, according to the data

October 27, 2021, 7:15 PM UTC

On Tuesday, after long deliberation and several mentions that this was the most difficult vote it had faced, an advisory committee to the FDA voted 17 to one (an abstention) in favor of recommending the Pfizer/BioNTech COVID-19 vaccine for use in children ages 5 to 11.

The vote came down to a debate over whether the benefits of the vaccine in preventing COVID-19 cases, hospitalizations, and deaths in young children outweighed the risks of potential side effects, namely myocarditis. 

On face value, the safety and efficacy data presented by Pfizer were strong. Children in the clinical trial produced similar antibody levels as adolescents and young adults did, despite the fact that the dose used in 5- to 11-year-olds was one-third of that given to those age 12 and up. There were three cases of symptomatic COVID-19 in the vaccinated group and 16 cases in the placebo group, which equates to a 90.7% efficacy rate. Asymptomatic cases were not measured in the study, and there were no instances of severe COVID-19 or the inflammatory syndrome MIS-C in either group.

In terms of safety data, 70% to 75% of children who received the vaccine experienced pain at the injection site, which was the most common side effect. So-called systemic effects, such as fever, headache, and chills, were lower in children than they were in young adults and peaked at roughly 40% of the vaccine group experiencing fatigue after the second dose. There were no serious side effects related to the vaccine (the few that did occur were from normal childhood accidents, like fracturing a bone or swallowing a “foreign body”). 

The most intense topic of discussion was a side effect that didn’t occur during the clinical trial: myocarditis. Inflammation of the heart muscle in the days following vaccination has emerged as a serious side effect of concern, particularly in young men under the age of 25. According to the Vaccine Adverse Event Reporting System (VAERS), there have been 877 cases of myocarditis out of more than 3.5 million vaccine doses given. In the highest risk group, males age 16 and 17, the case rate is 0.007%. In other words, the risk of vaccination-induced myocarditis is extremely low. What’s more, nearly all cases have recovered quickly without any lingering concerns. 

It’s unknown what the risk of myocarditis from vaccines will be for younger children. Matthew Oster, a pediatric cardiologist at Emory University, presented data on general myocarditis risk broken down by age and sex. Most cases of myocarditis are caused by a viral or bacterial infection, or they’re the result of a medication or immunological condition. Notably, children ages 5 to 11 have the lowest instances of myocarditis overall, with an annual incidence of 0.8 per 100,000. In contrast, children ages 5 to 11 are at the highest risk of developing MIS-C from COVID-19, and myocarditis occurred in roughly 9% of cases of MIS-C.

Compared with adults, children have a relatively low risk of developing severe disease or dying from COVID-19. But the risk is not zero. Fiona Havers, a member of the CDC Epidemiology Task Force, presented data on how children have been affected by the pandemic. She reported that more than 8,300 children ages 5 to 11 have been hospitalized for COVID-19 since the beginning of the pandemic, approximately two-thirds of whom had an underlying condition, the most common being asthma and obesity. Hospitalization rates for Black, Hispanic, and Native American children are three times as high as those for white children.

A secondary impact discussed was the educational and sociological loss children experienced as a result of school closures. Between August and October 2021, there were 2,074 schools closed because of COVID-19, impacting 1,069,116 students. Interestingly, screens to detect SARS-CoV-2 antibodies in the population, indicating a prior infection with the virus, suggest that 42% of children ages 5 to 11 have already come into contact with the virus.

It was this debate over the known low risk from COVID-19 versus the potential low risk from myocarditis that most consumed the committee. Some members, like Hayley Gans, a pediatric infectious disease specialist at Stanford University, thought that the risk of myocarditis would be even lower in the younger age group, both because they were generally at a reduced risk and because the vaccine dosage they would be given is smaller. 

Similarly, Amanda Cohn, chief medical officer at the National Center for Immunizations and Respiratory Diseases, stated that the known risks, such as the 94 children who had died from COVID-19, outweighed the hypothetical ones posed by myocarditis. And, as she pointed out, the U.S. health care system regularly vaccinates against diseases that have even fewer pediatric deaths and hospitalizations, such as the flu.

However, other members, such as Michael Kurilla, an infectious disease expert at the National Institutes of Health and the lone abstention in the vote, argued that because such a high percentage of the population had already been exposed to the virus, the benefit offered by vaccinating all children would be quite low.

Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, summed up the sentiment for many members when he said that it was “nerve-racking” to make a decision for millions of children based on data from only a few thousand. “You never know everything,” he said. The question is, “When do you know enough?”

Ultimately, the committee decided that they knew enough to recommend making the vaccine available to the families who wanted it for their children, especially kids who have an underlying condition that places them at greater risk for severe disease. Several members cautioned against vaccine mandates, though, which could be implemented by school districts. Next, the CDC advisory committee will meet to determine whether any additional recommendations should be made regarding who should—or should not—be eligible for the vaccine. Once that final step is complete, vaccines could be made available for children as early as next week.

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