Skip to main content

Dr. Mayank Amin puts a band-aid on 10-year-old Ernest Jones after administering a Pfizer-BioNTech COVID-19 booster vaccine at Skippack Pharmacy in Schwenksville, Penn., on May 19.HANNAH BEIER/Reuters

Drugmakers Pfizer Inc. and BioNTech SE said on Monday that three doses of their COVID-19 vaccine generated a strong immune response in children under age five and was safe and well-tolerated in their clinical trial.

The companies said they plan to soon ask global regulators to authorize the shot for the age group, children for whom no vaccine is currently approved in most of the world. They said they expect to complete their submission of data to the U.S. Food and Drug Administration (FDA) this week.

The clinical trial involved giving 1,678 children ages six months to under five years smaller doses of the vaccine than given to older children and adults. Pfizer and BioNTech said that three shots of a three-microgram formulation of their vaccine generated a similar immune response in that age group as in 16- to 25-year-olds who had received two doses of the 30-microgram formulation of the vaccine in an earlier clinical trial.

“The study suggests that a low three-microgram dose of our vaccine, carefully selected based on tolerability data, provides young children with a high level of protection against the recent COVID-19 strains,” BioNTech chief executive Ugur Sahin said in a statement.

Rival vaccine maker Moderna Inc. released trial data in March showing that its vaccine was safe and generated a similar immune response in young children as for adults.

New York-based Pfizer Inc. and Germany-based BioNTech said that an early analysis of 10 symptomatic COVID-19 cases identified through April 29, while the Omicron variant was dominant, suggested a vaccine efficacy of 80.3 per cent in the under-five age group. This analysis was not conclusive, as the trial’s protocol specified that efficacy should be calculated based on at least 21 cases.

Pfizer and BioNTech said final efficacy data in the age group will be made public when it is available.

The drugmakers had previously tested two doses of the three-microgram vaccine in the children. But the two-dose trial failed to meet its primary endpoint after results for children ages two to four showed a weaker immune response than in adults.

The trial participants received their third dose at least two months after their second shot. Pfizer said the vaccine was well tolerated, with most adverse side effects being mild or moderate.

The Pfizer/BioNTech shot is currently authorized for use in all Americans ages five and older. Children ages five to 11 receive two 10-microgram doses as their primary course, while people ages 12 and older receive two 30-microgram doses.

It was not clear how many American parents will vaccinate their children in the age group. Only 29 per cent of American children ages five to 11 are fully vaccinated and COVID-19 is generally more mild in children than adults.

U.S. regulators are already preparing to review the data in younger children, as well as data submitted by Moderna for children under age six. The FDA said on Monday that a committee of its external advisors will meet on June 15 in order to consider the use of the two vaccines in the youngest children.

Moderna has said two 25-microgram shots of its vaccine were around 37 per cent effective in preventing infections in children ages two to five and 51 per cent effective for children ages six months to two years.

Our Morning Update and Evening Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.