A two-dose regimen of the messenger RNA COVID-19 vaccine Comirnaty showed a favorable safety profile and robust neutralizing antibody responses in children 5 to 11 years of age, according to trial results released by the vaccine’s developer, Pfizer-BioNTech.

These are the first results reported from this pivotal trial in this age group.

The children in this age group were given two doses of 10-mcg 21 days apart, rather than the 30-mcg dose used for people 12 years of age and older.

The phase 1/2/3 trial initially enrolled up to 4,500 children 6 months to 11 years of age in the United States, Finland, Poland and Spain from more than 90 clinical trial sites. It was designed to evaluate the safety, tolerability and immunogenicity of the Pfizer-BioNTech vaccine on a two-dose schedule (approximately 21 days apart) in three age groups: 5 to 11 years; 2 to 5 years; and 6 months to 2 years.

Based on the phase 1 dose-escalation portion of the trial, in the phase 2/3 study children 5 to 11 years of age received a two-dose schedule of 10 mcg each, while children younger than 5 received a lower 3-mcg dose for each injection. The trial enrolled children with or without prior evidence of SARS-CoV-2 infection.

The data released from the phase 2/3 study was on 2,268 children 5 to 11 years of age who received the two-dose schedule. In the trial, the SARS-CoV-2–neutralizing antibody geometric mean titer (GMT) was 1,197.6 (95% CI, 1,106.1-1,296.6), demonstrating strong immune response in this cohort one month after the second dose. This compares well with the GMT of 1,146.5 (95% CI, 1,045.5-1,257.2) from participants 16 to 25 years of age, who were used as the control group for this analysis and were administered a two-dose regimen of 30 mcg, according to Pfizer-BioNTech.

The COVID-19 vaccine also was well tolerated, with side effects generally comparable with those observed in participants 16 to 25 years of age.

Pfizer-BioNTech said they carefully selected the 10-mcg dose for safety, tolerability and immunogenicity in children 5 to 11 years of age.

in a press release, Pfizer-BioNTech noted that “since July, pediatric cases of COVID-19 have risen by about 240% in the U.S.—underscoring the public health need for vaccination. These trial results provide a strong foundation for seeking authorization of our vaccine for children 5 to 11 years old.”

Pfizer-BioNTech plans to share these data with the FDA, European Medicines Agency (EMA) and other regulators as soon as possible. For the United States, the data is expected to be included in a near-term submission for emergency use authorization as safety and efficacy data required to file for full FDA approval in this age group continue be generated. A request to the EMA to update the EU conditional marketing authorization also is planned.

—IDSE Staff