Three-Dose Pfizer Vaccine Spurs Strong Response in Youngest Children

MONDAY, May 23, 2022 (HealthDay News) -- Pfizer/BioNTech says a three-dose regimen of its COVID-19 vaccine appears to provoke a strong immune response in the youngest age group of children -- those aged 6 months to 5 years.

This is the only age group not yet approved for COVID-19 vaccination by the U.S. Food and Drug Administration. Pfizer said it plans to submit its new data to the agency this week.

The phase 2/3 trial involved almost 1,700 children who received a third child-sized dose of the vaccine during a time when the omicron variant was dominant. Tests conducted a month afterward showed an antibody response that was similar to that seen in 16- to 25-year-olds who got two doses of vaccine.

Midway through the trial, the third dose gave the young children 80 percent protection against asymptomatic COVID-19. The researchers spotted 10 symptomatic cases of COVID-19 arising at least seven days after the third dose. But the Pfizer team stressed that their analysis cannot be completed until at least 21 symptomatic cases arise in the vaccinated group and are then compared to the number of symptomatic cases in the unvaccinated group.

The vaccine doses were adjusted downward for these smallest children -- three 3-mcg doses for those aged 6 months to 5 years. That is compared to two 10-mcg doses for children aged 5 to 12 years and two 30-mcg doses for people 12 years and older. Children in the youngest age group get the first two doses three weeks apart and a third dose two months later. There appeared to be no safety issues with the vaccine, which was well tolerated by the children.

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