Pfizer/BioNTech COVID-19 vaccine produces strong immune response in children

Pfizer and BioNTech have announced recent data from a top-line safety, immunogenicity and vaccine efficacy phase 2/3 trial assessing a third 3µg dose – one-tenth of the adult dosage – of their COVID-19 vaccine for children aged from six months to under five years old.

The vaccine resulted in a strong immune response following the third dose in this particular age group, and showed a positive safety profile similar to placebo.

One of the second endpoints in the trial was vaccine efficacy, which was 80.3% in children aged six months to under five years. This analysis was taken during a period when the Omicron strain was the predominant variant, and was based on ten symptomatic COVID-19 cases identified seven days after the third dose and accrued as of 29 April 2022.

In the phase 2/3 trial, more than 10,000 children aged six months to under 12 years were enrolled at more than 90 clinical trial sites in the US, Finland, Poland and Spain. 1,678 children were given a third dose of the 3µg formulation at least two months after the second dose, when Omicron was the most prevalent strain.

It was found that this dosage of the Pfizer/BioNTech COVID-19 vaccine was well tolerated in the age group, and no new safety signals were identified, while most adverse events were noted as being mild to moderate. The immunogenicity, safety and vaccine efficacy data for three doses of the vaccine in children under 5 years of age remain consistent with the data shown in adults.

Albert Bourla, chairman and CEO, Pfizer, said: “Our COVID-19 vaccine has been studied in thousands of children and adolescents, and we are pleased that our formulation for the youngest children, which we carefully selected to be one-tenth of the dose strength for adults, was well tolerated and produced a strong immune response.”

A formal analysis will be performed – as dictated by trial protocol – when at least 21 cases have been identified seven days after the third dose, with the final efficacy data shared publicly as and when available.

In February 2022, Pfizer and BioNTech started a rolling submission for an Emergency Use Authorization (EUA) of their COVID-19 vaccine in children aged six months to under five years, after a request was made by the US Food and Drug Administration (FDA). During which time, a two-dose series was determined to be well tolerated in this age group.

The companies aim to submit the new data on three doses to the rolling US EUA application this week, while submissions to regulators globally will follow.