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Pfizer said Thursday it wants to expand its COVID-19 booster shots to healthy elementary-age kids. U.S. health authorities already urge everyone 12 and older to get one booster dose for the best protection against the newest variants -- and recently gave the option of a second booster to those 50 and older. Now Pfizer says new data shows healthy 5- to 11-year-olds could benefit from another kid-sized shot. (Neergaard, 4/14)

A booster dose of the Pfizer-BioNTech Covid-19 vaccine raised antibody levels in children ages 5 to 11, the company said Thursday. The additional shot, given six months after the two-dose primary series, led to a sixfold increase in antibodies against the original strain of the coronavirus. The clinical trial of the booster shot included 140 children ages 5 through 11. In a smaller sub-analysis of 30 kids in the trial, Pfizer said the additional dose led to a thirtysixfold increase in antibodies against the omicron variant of the virus. (Miller, 4/14)

Blood samples from 30 children showed a 36-fold increase in antibodies against the omicron variant after receiving the third shot. In 140 children, a third dose also increased antibodies six-fold against the original strain of the virus. Because the vaccine is already approved in adults, regulators have allowed immune responses to be used as a metric of effectiveness, instead of actual infections. No new safety issues arose among the 400 children in the booster trial. The positive results "reinforce the potential function of a third dose of the vaccine in maintaining high levels of protection against the virus in this age group," according to a Pfizer news release. (Weintraub, 4/14)

Studies in adults show that while a third shot increases the level of antibodies, it also hones those antibodies’ ability to block an array of variants — a process called “affinity maturation.” The data on a booster in 5-to-11-year-olds has not been published or peer-reviewed, but it echoes those findings. Like other booster trials, this study did not measure the ability of the vaccine to stop people from becoming ill but was based on laboratory measurements of the booster’s ability to increase antibodies in their blood. (Johnson, 4/14)