The "stealth omicron" subvariant has now spread to 47 U.S. states, a study finds vaccination during pregnancy can protect infants from Covid-19 hospitalization, and more in this week's roundup of Covid-19 news.

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• FDA last week authorized a new monoclonal antibody drug from Eli Lilly. The drug, which is called bebtelovimab, is intended to treat patients with mild-to-moderate symptoms who are at high risk of severe Covid-19. According to FDA, the drug should be used in patients "for whom alternative Covid-19 treatment options ... are not accessible or clinically appropriate." It is the second monoclonal antibody—in addition to Vir Biotechnology and GlaxoSmithKline's sotrovimab—that is shown to work against the omicron variant. "Today's action makes available another monoclonal antibody that shows activity against omicron, at a time when we are seeking to further increase supply," said Patrizia Cavazzoni, director of FDA's Center for Drug Evaluation and Research. The federal government has agreed to purchase 600,000 courses of bebtelovimab for at least $720 million, with shipments expected to begin this month, STAT News reports. The contract also includes an option to purchase an additional 500,000 courses by July 31, Lilly said. (Chen, Axios, 2/11; Joseph, STAT News, 2/11; Loftus, Wall Street Journal, 2/11)

• Novavax last week announced that its protein-based Covid-19 vaccine was safe and effective for children ages 12 to 17. In a trial of 2,247 adolescents, which took place between May and September 2021 in the United States, the two-dose vaccine was 82% effective at preventing infection. According to Becker's Hospital Review, Novavax will submit apply for authorization of its vaccine in adolescents in the first quarter of 2022. The company also plans to test the vaccine in younger children later this year. Currently, FDA is reviewing use of Novavax's Covid-19 vaccine in adults. Several countries, including Britain, and the World Health Organization have already authorized the vaccine for use in adults. (Carbajal, Becker's Hospital Review, 2/11; AP/Modern Healthcare, 2/11; Gonzalez, Axios, 1/31)

• A CDC study released last week found that immunity against Covid-19 from booster doses declined substantially after around four months—although protection against hospitalization remained significant. For the study, researchers examined 241,204 ED/urgent care center visits and 93,408 hospitalizations in 10 states from August 2021 to Jan. 22, 2022, covering periods when delta and omicron were dominant. Around 10% of people in the study were boosted. Overall, researchers found that booster protection against hospitalization from the omicron variant declined from 91% after two months to 78% after four months. In addition, protection against ED or urgent care visits declined from 87% to 66% after four months. According to The Hill, these findings of waning immunity from boosters could inform discussions about the potential necessity of additional shots. Anthony Fauci, director of the National Institutes of Allergy and Infectious Diseases, said the federal government is monitoring data on protection against hospitalization to decide whether an additional booster dose is needed. "There may be the need for yet again another boost—in this case, a fourth-dose boost for an individual receiving the mRNA [vaccine]—that could be based on age, as well as underlying conditions," he said. (Sun, Washington Post, 2/11; Mandavilli, New York Times, 2/11; AP/Modern Healthcare, 2/11; Sullivan, The Hill, 2/11)

• The "stealth omicron" or BA.2 omicron subvariant has now spread to at least 74 countries and 47 U.S. states, according to data from outbreak.info. In the United States, CDC data shows the subvariant is most prevalent in HHS' region 3, which includes Pennsylvania, West Virginia, Virginia, Delaware, and Maryland. Currently, the subvariant accounts for 3.9% of all Covid-19 cases in the United States, while the original BA.1 omicron variant accounts for 73.2% of cases. Recent data suggests that the BA.2 subvariant is more transmissible than the original BA.1 variant. However, a new study from South Africa indicates that the subvariant has a similar level of severity to the original, Bloomberg reports. For the study, researchers from the country's National Institute for Communicable Diseases analyzed almost 100,000 Covid-19 cases from a large hospital group and a government laboratory service and found that patients infected with the subvariant had similar rates of severe disease and hospitalization as those infected with the original omicron variant. Although the researchers cautioned that the findings may not be applicable to other countries considering South Africa's immune make up, they said the data was "reassuring" since "the clinical profile of illness remains similar." (Gleeson, Becker's Hospital Review, 2/16; Sguazzin, Bloomberg, 2/16)

• Covid-19 vaccination during pregnancy may help protect infants from the coronavirus, according to a new CDC study. For the study, researchers examined 379 infants under six months who had been admitted to one of 20 U.S. pediatric hospitals between July 1, 2021, and Jan. 17. Of the infants, 176 tested positive for Covid-19 and had either been admitted for the disease or had symptoms of it. Overall, researchers found that Covid-19 vaccination was 61% effective at protecting infants from hospitalization with the disease. Vaccination later during a pregnancy was also associated with greater protection (32% in the first 20 weeks vs. 80% later), the researchers found, but they emphasized that pregnant individuals should generally get vaccinated as soon as possible. "Maternal vaccination is a really important way to help protect young infants," said Dana Meaney-Delman, a CDC researcher. (Anthes, New York Times, 2/15; Sullivan, The Hill, 2/15)