The Food and Drug Administration’s (FDA) advisory committee voted unanimously on June 14 to recommend the emergency-use authorization (EUA) of Moderna’s COVID-19 vaccine for children ages six to 17 years. If it’s also recommended by the U.S. Centers for Disease Control and Prevention (CDC), Moderna’s will be the second COVID-19 vaccine available to this age group. (The FDA and CDC had previously approved an EUA to Pfizer BioNTech’s COVID-19 vaccine for children 5 years old and above in October 2021.
Because the company submitted data that broke down the children into two age groups—from six to 11 years old, and 12 to 17 years old—the 22-member panel voted separately for the two populations. Every vote unanimously affirmed that vaccination was worth the risk.
The committee’s recommendation is based on data submitted by Moderna’s scientists on the safety and efficacy of its two-dose vaccine for kids ages 6-17. Those studies found that the vaccine—which is the same one authorized for adults but in a smaller dose—is as effective at protecting children from getting seriously ill or dying from COVID-19 as it is at protecting adults, even against different variants of the virus.
The FDA’s panel of pediatric and immunology experts reviewed two studies conducted by Moderna in children, which showed that kids ages six to 17 generated levels of virus-neutralizing antibodies one month after their second dose that were equal to those produced by older adolescents and adults. Because the pediatric studies did not include a long follow-up time, FDA scientists inferred from this data that those levels of antibodies—measured one month after the second dose—would be sufficient to protect children from severe disease by comparing them to antibody levels generated by adults. Study after study has demonstrated that those with similar levels of neutralizing antibody are 90% less likely to be hospitalized, become severely ill, or suffer from COVID-19. The studies showed that no children were diagnosed with COVID-19-related severe illness or death.
Moderna’s pediatric vaccine comes in two different doses, depending on children’s ages. The dose for older children, 12-17 year olds, would be 100 micrograms. Children ages six to 11 would receive half that dose in each of their two shots; the company’s studies found that the lower dose led to sufficient levels of virus-fighting antibodies and lowered the risk of potential side effects.
Panel members considered the issue of vaccine efficacy. This is because different factors apply to different age groups. Because Moderna tested its vaccine in children moving from the oldest to the youngest—and only vaccinated younger children after the shot proved to be safe in older kids—the variants to which the children might have been exposed changed over time. The majority of participants had been enrolled in the U.S. and there were waves of SARS-CoV-2 variants that swept across the country during each age group’s testing. Data on vaccine effectiveness in adults to compare with vaccine efficacy among children was also available before variants were developed. They reflect immunity to the original SARS/CoV-2 virus.
For children aged between 12 and 17 years, the vaccine effectiveness against COVID-19 symptoms was 93%. The original SARS CoV-2 strain and its first variant, Alpha were in circulation. Children six to 11 years of age who received vaccines during the Delta wave had an efficacy rate of 76.8%. The vaccine efficacy for children aged 2-5 years who had been tested during the Omicron wave was 36.8%, while it was 51.6% in toddlers 6 months to 2 years. This data is similar to the ones found for adults who were vaccinated during all variant waves.
Some members of the committee—including Dr. Paul Offit, professor of pediatrics at the Children’s Hospital of Philadelphia—raised concerns that the lower efficacy against Omicron would mean that children, like adults, would need an additional dose to maintain immunity at sufficient levels to protect them against serious disease. “This is a three-dose vaccine if it is to be effective against serious Omicron disease,” he said. But the members of the panel did not vote on the question about how many doses were sufficient to provide protection. Their task was to weigh the benefits and risks of Moderna’s two-dose series to determine if those are safe and effective.
In its review of the data, the FDA’s scientists determined that the vaccine was safe for kids ages 6-17, with similar types and rates of adverse reactions as those reported among adults. The safety of the vaccines was one reason why the FDA delayed reviewing Moderna’s vaccine data for this age group, which were submitted in June 2021. After Moderna submitted this data, studies showed that adolescents who were vaccinated with Moderna’s shot in the U.S. and other countries—including in the U.K., Europe, and Canada—had a two to seven-fold higher risk of developing dangerous inflammation of the heart tissues, known as myocarditis,Comparing to children vaccinated with Pfizer-BioNTech’s shot, which is made with similar mRNA technology and was authorized in the U.S. in May 2021. The risk appeared highest among young males between ages 18 and 24, and the CDC launched an investigation to determine if Moderna’s vaccine posed any higher risk compared to Pfizer-BioNTech’s. The most recent data from CDC’s database that monitors side effects through May 2022 “do not support a difference in myocarditis/pericarditis risk for [Moderna’s vaccine] compared to [Pfizer-BioNTech’s vaccine],” the FDA review determined.
Moderna also asked for authorization to its vaccine at lower doses for children aged six months to six years. This request will be reviewed by the FDA Committee on June 15. The FDA committee will review the data Pfizer BioNTech has provided about vaccines in similar age groups, ranging from six months to four year old, during that meeting.
Having two vaccines for the pediatric population would provide more choice for parents eager to get their children vaccinated, and also potentially create more confusion if pediatricians or hospitals and pharmacies only stock one manufacturer’s shots. Although studies in adults have demonstrated that mixing and matching the two mRNA vaccines from Moderna and Pfizer BioNTech is effective and safe, those same studies are not yet applicable to children. However, experts believe that they can safely be used in pediatric populations.
If the CDC panel also recommends the Moderna vaccine for this pediatric population, the U.S. government says doses could be shipped to hospitals, doctors’ offices, and pharmacies beginning the week of June 20.
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