Pfizer-BioNTech sees favorable results for third dose COVID-19 vaccine in children 6 months to 5 years


Pfizer-BioNTech reports strong immune response, high efficacy, and favorable safety in third dose of the COVID-19 vaccine.

Pfizer-BioNTech today announced topline safety, immunogenicity, and vaccine efficacy data from its phase 2/3 clinical trial evaluating a third 3-µg dose of the COVID-19 vaccine in children 6 months to under 5 years old.

According to Pfizer, the phase 1/2/3 trial has enrolled more than 10,000 children aged 6 months to under 12 years in the United States, Finland, Poland, and Spain from over 90 trial sites. The trial evaluated the safety, tolerability, and immunogenicity of 3 doses of their COVID-19 vaccine in collaboration with BioNTech in 3 separate age groups. The age groups evaluated included ages 5 to under 12 years old, 2 to under 5 years old, and 6 months to under 2 years old.

In phase 1 of the trial, which was the dose-escalation potion of the trial, children 5 years old to under 12 received a 2-dose schedule of 10-µg each. In phase 2/3, children under 5 years old received a lower 3-µg dose for each injection—3 doses in total. The trial enrolled children with or without prior evidence of SARS-CoV-2 infection, according to the Pfizer press release announcing the results.

In phase 2/3, 1678 children received a third dose of the 3-µg formulation at least 2 months after the second dose at a time when the Omicron variant of the COVID-19 infection was predominant. Investigators examined immunogenicity using a geometric mean titer (GMT) ratio. Additionally, a seroresponse rate was conducted on a subset of participants 1 month after receiving the third dose in children under 5 years compared to the second dose in the 16- to 25-year-old population. Pfizer reported that non-inferiority was met in both the 6- to 24-month-old population and the 2- to under 5-year-old population for both coprimary end points.

The secondary end point of vaccine efficacy saw an 80.3% rate in children 6 months to under 5 years old. Investigators have concluded that three 3-µg doses in this age group was well-tolerated and no new safety signals were identified. Reported adverse events were mild to moderate.

Pfizer-BioNTech plan to submit new data on the 3-dose series to the United States Emergency Use Authorization application this week, with additional submissions to worldwide regulators to follow.


Pfizer-BioNTech COVID-19 vaccine demonstrates strong immune response, high efficacy and favorable safety in children 6 months to under 5 tears of age following third dose. Pfizer. Published May 23, 2022. Accessed May 23, 2022.

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