Explainer: Things to know about COVID vaccines for young children

May 31 (Reuters) – Advisors to the US Food and Drug Administration are scheduled to meet in June to decide whether to recommend approval of Moderna Inc’s (MRNA.O) vaccine for children under the age of 6 and Pfizer Inc’s ( PFE.N) and the COVID-19 vaccine from BioNTech SE (22UAy.DE) for children under 5 years of age. Continue reading

Here’s a look at some of the factors likely to be considered in this decision regarding the last age groups not yet covered by previous US regulatory approvals for COVID-19 vaccines.


Moderna has submitted an application to the FDA for approval of a two-dose regimen of its vaccine, called Spikevax, for children ages 6 months to 6 years. Pfizer has not yet completed its FDA submission, but its clinical trial tested a three-dose regimen of the vaccine in children ages 6 months to less than 5 years.

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Moderna plans to use a dose of 25 micrograms in this age group, which is lower than the 100 micrograms used in the first two doses in adults and the 50 micrograms used as a booster dose for non-immunocompromised adults. In its clinical study, Moderna administered the two doses 28 days apart.

Pfizer and BioNTech’s vaccine, called Comirnaty, was tested as a 3-microgram formulation in children under 5 years of age, compared to the 10-microgram version used in children aged 5 to 11 and a 30-year trial -Microgram dose used for people 12 years and older. In their clinical study, children received the first two doses about three weeks apart, with the third dose given at least three months after the second.

Lower dose versions are expected to reduce any side effects associated with the vaccines.


For the Moderna vaccine in a clinical trial involving approximately 6,700 children, efficacy in preventing symptomatic infections in children aged 6 months to 2 years was 43.7%, while efficacy in children aged 2 to 6 years was 37, was 5%.

There were not yet enough symptomatic cases of COVID-19 among the children in the Pfizer-BioNTech study to provide a definitive efficacy number. An early analysis based on 10 symptomatic COVID-19 cases identified when the Omicron coronavirus variant was dominant indicated a vaccine efficacy of 80.3% in the under 5 age group. Pfizer and BioNTech plan to update those numbers after at least 21 children in the study contracted symptomatic COVID-19.


Safety data, which included 1,678 children in Pfizer’s study, showed that side effects were generally comparable to those seen in adults. Pfizer said it chose the lower-dose 3-mcg version because of its safety profile. Although it didn’t disclose specific safety data, it said the vaccine was generally as safe at this dose as the placebo used in the study.

Moderna’s data showed that all side effects were mostly mild and moderate in severity, with a fever temperature similar to that seen after vaccination with other pediatric vaccines. Fever greater than 104 degrees Fahrenheit has been observed in 0.2% of children aged 2 to 6 years and 2 months to 2 years.

According to Moderna, there were no reports of myocarditis or pericarditis in its study, types of heart inflammation that have been linked to mRNA vaccines in rare cases in young men.

The US Centers for Disease Control and Prevention, based on data from the Pfizer vaccine, said rates of heart inflammation in boys aged 5 to 11 were much lower than in adolescents and young men.


If immunizations in these age groups receive regulatory approval, parents will have to decide whether to vaccinate their children. One question they might have is whether it’s worth it considering many young children were infected during the Omicron wave. Experts have said that natural immunity declines over time. Data has shown that among older children and adults, those who had an infection and received a booster shot had the greatest protection against COVID-19, according to Dr. Matthew Harris, a pediatric emergency medicine physician at Northwell Health in New York.

Vaccines also protect against hospitalizations and deaths, Harris said, listing these important reasons parents should consider vaccinating their children.

The FDA has set June 15 as the date to review approval of the Moderna and Pfizer/BioNTech vaccines for these age groups.

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Reporting by Manas Mishra in Bengaluru; Additional reporting by Mike Erman in Maplewood, New Jersey; Editing by Will Dunham

Our standards: The Thomson Reuters Trust Principles.

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