Covid-19 vaccine for 5- to 11-year-olds is safe and shows 'robust' antibody response, Pfizer says

In a highly anticipated announcement, Pfizer said on Monday a Phase 2/3 trial showed its Covid-19 vaccine was safe and generated a "robust" antibody response in children ages 5 to 11.

These are the first such results released for this age group for a US Covid-19 vaccine, and the data has not yet been peer-reviewed or published. Pfizer said it plans to submit to the US Food and Drug Administration for emergency use authorization soon. FDA officials have said that once data is submitted, the agency could authorize a vaccine for younger children in a matter of weeks.

The trial included 2,268 participants ages 5 to 11 and used a two-dose regimen of the vaccine administered 21 days apart. This trial used a 10-microgram dose -- smaller than the 30-microgram dose that has been used for those 12 and older.

"The 10 microgram dose was carefully selected as the preferred dose for safety, tolerability and immunogenicity in children 5 to 11 years of age," Pfizer said in a news release.

Participants' immune responses were measured by looking at neutralizing antibody levels in their blood and comparing those levels to a control group of 16- to 25-year-olds who were given a two-dose regimen with the larger 30-microgram dose. Pfizer said the levels compared well with older people who received the larger dose, demonstrating a "strong immune response in this cohort of children one month after the second dose."