Clinical trial studies show third injection boosts antibody levels higher than before the second dose.

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, the New York Times reports.

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 F.D.A. ahead of a two-day meeting of the agency’s outside advisory committee, scheduled for Thursday and Friday. In its own briefing document for the committee, also released Tuesday, the F.D.A. summarized the data without taking a position.

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.

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