Pfizer Reports Over 80% Efficacy for Third Dose of COVID-19 Vaccine in Children Under 5, Seeks FDA Emergency Use Authorization

On Monday, May 23, Pfizer, Inc. released data from an initial clinical trial evaluating the third dose of a 3-microgram Pfizer/BioNTech COVID-19 vaccine in children aged 6 months to 5 years. The results showed that the third dose elicited a strong immune response with an efficacy of 80.3%. The vaccine was well-tolerated by the children, and most side effects were mild to moderate.

Pfizer CEO Albert Bourla said in a statement: "We are pleased with the formulation we have developed for our youngest children, which is carefully selected at one-tenth the dose strength of the adult dose, well-tolerated, and generates a robust immune response. We look forward to completing submissions to regulatory authorities around the world as soon as possible, hoping to make this vaccine available to young children promptly upon receiving regulatory authorization." BioNTech CEO Ugur Sahin said that the company plans to complete their application this week, requesting Emergency Use Authorization (EUA) from the U.S. Food and Drug Administration (FDA) for the vaccine.

Hours after Pfizer released its data, the FDA announced that its independent vaccine expert committee would meet on June 15 to discuss applications from Pfizer and Moderna to authorize their vaccines for infants to preschool-aged children. This authorization would open up the last major market for COVID-19 vaccines, amid a current global surplus of adult-dose vaccines, and could pave the way for long-term revenue for vaccine developers if it becomes part of the childhood immunization program.

FDA originally planned to evaluate Pfizer's two-dose vaccine in February, but data showed it did not elicit a sufficiently strong immune response in children aged 2 to 4 years. The FDA then requested to review the results of the third dose trial. According to new data, 1,678 children received a third dose at least two months after the second dose during a period when Omicron was the predominant variant.

Children under the age of 5 are the only group in the U.S. who are not yet eligible for vaccination. According to data from the U.S. Centers for Disease Control and Prevention (CDC), during the large-scale Omicron infection wave in winter, the proportion of children under 5 being hospitalized was five times higher than during the peak of the pandemic. As of February, about 75% of children under 11 had been infected with COVID-19, according to the CDC. Currently, most countries have not yet approved COVID-19 vaccines for children under 5, and many parents are concerned about whether the vaccines are safe for young children.

Since 2022, the eligible scope of Pfizer's COVID-19 vaccine booster has been continuously expanding. In January, the vaccine was approved for use as a single booster dose for individuals aged 12 to 15 who have completed two doses of Pfizer vaccine, with a dosage of 30 micrograms. Not long ago, on May 17 local time, the FDA revised the emergency use authorization for Pfizer's COVID-19 vaccine, approving a booster dose of Pfizer vaccine for children aged 5 to 11 who have completed two doses of Pfizer vaccine, at least five months after the second dose, with a dosage of 10 micrograms.

Moderna, Pfizer's rival, applied for emergency use of its COVID-19 vaccine with the FDA at the end of April this year, targeting children aged 6 months to 5 years. Trial data released by Moderna in March showed that its vaccine is safe and generates an immune response in young children similar to that in adults. The company stated that two doses of 25 micrograms of the vaccine are approximately 37% effective in preventing infections in children aged 2 to 5, and 51% effective in children aged 6 months to 2 years.