In documents released Tuesday morning, Moderna argued that the Food and Drug Administration should authorize a half-dose of its coronavirus vaccine as a booster shot for recipients at least six months after the second dose, citing evidence that the vaccine’s potency against infection wanes over time.

Moderna cited the rate of breakthrough infections, “real world evidence of reduced effectiveness against the delta variant,” and falling levels of neutralizing antibodies from its vaccine six to eight months after a second dose. The company said its clinical trial studies showed that a third injection boosted antibody levels — one measure of the immune system’s response — higher than what they had been before the second dose.

The documents were released by the FDA before a two-day meeting of the agency’s outside advisory committee, scheduled for Thursday and Friday.

A nurse prepares a shot as a study of a possible COVID-19 vaccine developed by the National Institutes of Health and Moderna in Binghamton, N.Y. (Hans Pennink / The Associated Press, file)
FDA review finds Moderna’s booster dose of the coronavirus vaccine strengthens disease-fighting response

The committee is expected to vote on whether to recommend emergency authorization of booster shots of both Moderna’s and Johnson & Johnson’s vaccines. While the panel’s votes are not binding, regulators typically follow them.

Moderna did not try to argue that its vaccine is waning now against severe disease or hospitalization, and the existing data does not appear to support that claim. That distinguishes Moderna’s application from the one mounted by Pfizer-BioNTech last month.

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The FDA said the data show Moderna and the other vaccines “still afford protection against severe COVID-19 disease and death in the United States.”

The FDA and the Centers for Disease Control and Prevention decided to authorize emergency use of boosters for many but not all Pfizer-BioNTech vaccine recipients. The eligible include those who are 65 or older, who live in long-term care facilities, who have underlying medical conditions or who are at higher risk of exposure to the virus because of their jobs or institutional settings. The last group includes health care workers, teachers and prisoners.

In the document released Tuesday, the FDA proposed the outside experts consider essentially the same eligibility groups for Moderna recipients.

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