Novavax Inc. /zigman2/quotes/202614340/composite NVAX -3.61% said Monday that it asked the Food and Drug Administration to authorize its COVID-19 booster for adults. The company's primary series of protein-based shots received FDA authorization in July. "We believe our vaccine offers a broad, long-lasting immune response against a range of variants," Novavax CEO Stanley Erck said in a news release. Novavax said giving a third shot of its vaccine to adults six months after getting the first two Novavax shots boosted antibody levels that were comparable to or exceeded levels reported after the first two shots. Novavax's stock has declined 71.0% this year, while the broader S&P 500 /zigman2/quotes/210599714/realtime SPX -0.20% is down 10.2%.