The Phase 2/3 trial included 1,678 children who received a third dose of the vaccine during the period when the Omicron coronavirus variant was dominant. Antibody levels tested one month after the third dose showed the vaccine produced a similar immune response to two doses in 16- to 25-year-olds, the companies said. The data has not been peer reviewed or published in a professional journal.
Mid-trial results revealed an 80.3% vaccine efficacy against symptomatic Covid-19 in this young age group. The companies identified 10 symptomatic cases at least seven days after the third dose. However, the efficacy rate will not be finalized until at least 21 symptomatic cases are found in the vaccinated group and compared to the number of symptomatic cases in the placebo group.
The companies said three pediatric doses for this age group were “well tolerated” and no new safety signals were identified.
“These safety, immunogenicity and efficacy data are encouraging, and we look forward to completing our submissions to regulatory authorities around the world soon in hopes of making this vaccine available to young children as quickly as possible. subject to regulatory approval,” said Pfizer’s Chairman and Chief Executive Officer. Albert Bourla said in a statement.
Vaccine doses for these children are lower than those used in older age groups. People 12 years and older get two doses of a 30 microgram vaccine and children ages 5 to 12 get two doses of a 10 microgram vaccine. Both of these age groups are eligible for booster doses.
For children 6 months to 5 years old, the Pfizer/BioNTech vaccine consists of three doses of 3 micrograms. The two initial doses were given three weeks apart and the third dose was given at least two months after the second dose.
Dr. William Schaffner, a professor in the Division of Infectious Diseases at Vanderbilt University School of Medicine, said Monday that vaccine scientists were careful to adjust the dose for young children to achieve “a good effect with a minimal side effects.
“We consider this a three-dose vaccine, and preliminary data acquired in the Omicron era indicates that it is in fact 80% effective,” Schaffner told CNN’s Brianna Keilar. “We’ll want to look at this very carefully, but so far it’s good news.”
In February, the US Food and Drug Administration asked the companies to submit an emergency use authorization request based on the two-dose data, but then postponed a meeting of the vaccine advisory board of the agency so that data from the third dose can be taken into account.