Three Doses of Pfizer’s COVID-19 Vaccine Well Tolerated in Children Under 5 Years of Age

Topline data showed that a third dose of the Pfizer-BioNTech vaccine was well tolerated among children with a safety profile similar to placebo.

Three doses of Pfizer-BioNTech’s COVID-19 vaccine in children under 5 years of age produced a strong immune response and a favorable safety profile similar to placebo, according to topline data released by the manufacturers on Monday.

In a news release, the companies announced topline safety, immunogenicity, and vaccine efficacy data from a phase 2/3 clinical trial evaluating a third 3-µg dose of the COVID-19 vaccine in children aged 6 months to under 5 years.

“The study suggests that a low 3-µg 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,” said Ugur Sahin, MD, CEO and co-founder of BioNTech, in the May 23 press statement.

In the trial, 1678 children aged 6 months to under 5 years received a third dose of the 3-µg formulation of the vaccine at least 2 months after the second dose at a time when Omicron was the dominant variant. Pfizer noted that immunogenicity based on 3 doses was comparable to a 2-dose series in persons aged 16 to 25 years, and non-inferiority criteria were met for both the 6- to 24-month-old population and 2- to under 5-year-old population.

“Three 3-µg doses of the Pfizer-BioNTech COVID-19 Vaccine was well-tolerated in this age group, and no new safety signals were identified. The majority of adverse events were mild or moderate,” added Pfizer in the press release. According to the statement, the formulation for the youngest children is one-tenth of the dose strength used for adults.

Vaccine efficacy—the secondary endpoint in the clinical trial—was 80.3% in children aged 6 months to under 5 years. The manufactures noted, however, that vaccine efficacy was based on 10 symptomatic COVID-19 cases identified from 7 days after the third dose and accrued as of April 29, 2022. A formal analysis will be conducted after 21 cases have accrued per trial protocol, and final vaccine efficacy will be shared when available.

Pfizer and BioNTech plan to submit this topline data for the 3-dose series to the rolling US emergency use authorization application this week, and then to regulators globally afterward.

“We are preparing the relevant documents and expect completing the submission process to the FDA this week, with submissions to EMA and other regulatory agencies to follow within the coming weeks,” said Sahin.