Three-Dose Pfizer Vaccine the Charm for Toddlers

The three-dose formulation of Pfizer-BioNTech’s COVID-19 vaccine for kids under age 5 is safe and met immunobridging criteria, the manufacturers said on Monday.

And while it was not a primary endpoint, vaccine efficacy with the three doses of 3 μg was 80.3% based on a descriptive analysis of 10 symptomatic COVID cases 7 days after a third dose during a time period when Omicron was the dominant variant. (A formal analysis will be conducted after 21 cases have accrued.)

The primary analysis was based on 1,678 children ages 6 months to 4 years. Pfizer noted that immunogenicity based on three doses of the vaccine was comparable to a two-dose series in people ages 16 to 25, and non-inferiority criteria were met for both the 6 month to under 2-year population and the group of children ages 2 to 4 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 a statement.

Indeed, the manufacturers noted that the majority of adverse events were mild or moderate, and no new safety signals were identified.

Data were derived from a phase II/III study of more than 10,000 children ages 6 months to 11 years in the U.S., Finland, Poland, and Spain.

“The safety, immunogenicity and vaccine efficacy data for three doses of the vaccine in children under 5 years of age are consistent with the data seen in adults, suggesting that a third dose will provide similar benefit in children,” the manufacturers said.

They plan to seek an emergency use authorization (EUA) for this three-dose series, after the two-dose series failed to meet immunobridging endpoints and the FDA postponed the Vaccines and Related Biological Products Advisory Committee (VRBPAC) meeting back in February.

The agency announced that VRBPAC will discuss data from Pfizer-BioNTech for the vaccines in this age group on June 15, along with discussion of Moderna’s vaccine in children ages 6 months to 5 years.