23 May 2022 - - US-based pharmaceutical company Pfizer Inc. (NYSE: PFE) and German biotechnology company BioNTech SE (NASDAQ: BNTX) have posted topline safety, immunogenicity and vaccine efficacy data from a Phase 2/3 trial evaluating a third 3-µg dose of the Pfizer-BioNTech COVID-19 Vaccine in children 6 months to under 5 years of age, the companies said.

Following a third dose in this age group, the vaccine was found to elicit a strong immune response, with a favorable safety profile similar to placebo.

Vaccine efficacy, a secondary endpoint in this trial, was 80.3% in children 6 months to under 5 years of age.

This descriptive analysis was based on 10 symptomatic COVID-19 cases identified from seven days after the third dose and accrued as of April 29, 2022.

The trial protocol specifies a formal analysis will be performed when at least 21 cases have accrued from seven days after the third dose. Final vaccine efficacy data will be shared once available.

In the Phase 2/3 trial, 1,678 children received a third dose of the 3-µg formulation at least two months after the second dose at a time when Omicron was the predominant variant.

The immunogenicity analysis of geometric mean titer ratio and seroresponse rate was conducted on a subset of study participants one month following the third dose in children 6 months to under 5 years of age, compared to the second dose in the 16- to 25-year-old population.

Non-inferiority was met for both the 6- to 24-month-old population and the 2- to under 5-year-old population for both co-primary endpoints.

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.

Studies in adults, adolescents, and children over 5 years of age continue to indicate that three doses of the Pfizer-BioNTech COVID-19 Vaccine enhances protection compared to two doses.

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.

In February 2022, the companies initiated a rolling submission for Emergency Use Authorization of their COVID-19 vaccine in children 6 months to under 5 years of age, following a request by the US Food and Drug Administration.

At that time, a two-dose series was determined to be well-tolerated in this age group. Pfizer and BioNTech plan to submit these new safety, immunogenicity, and vaccine efficacy data on three doses to the rolling US EUA application this week, with submissions to regulators worldwide to follow.

The Pfizer-BioNTech COVID-19 Vaccine, which is based on BioNTech's proprietary mRNA technology, was developed by both BioNTech and Pfizer.

BioNTech is the Marketing Authorization Holder in the United States, the European Union, the United Kingdom, Canada and the holder of emergency use authorizations or equivalents in the United States (jointly with Pfizer) and other countries.

Submissions to pursue regulatory approvals in those countries where emergency use authorizations or equivalent were initially granted are planned.

The Phase 1/2/3 trial has enrolled more than 10,000 children ages 6 months to under 12 years of age in the United States, Finland, Poland, and Spain from more than 90 clinical trial sites.

The trial evaluated the safety, tolerability, and immunogenicity of three doses of the Pfizer-BioNTech COVID-19 Vaccine in three age groups: ages 5 to under 12 years; ages 2 to under 5 years; and ages 6 months to under 2 years.

Based on the Phase 1 dose-escalation portion of the trial, children ages 5 to under 12 years received a two-dose schedule of 10 µg each while children under age 5 received a lower 3 µg dose for each injection in the Phase 2/3 study.

The trial enrolled children with or without prior evidence of SARS-CoV-2 infection.

Pfizer-BioNTech COVID-19 Vaccine is FDA authorized under Emergency Use Authorization for active immunization to prevent coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in individuals 5 years of age and older.