The Biden administration buys an additional 200 million Moderna Covid-19 vaccine doses, a new study suggests the coronavirus may have arrived in the United States weeks prior to the first documented case, and more.

• AstraZeneca on Tuesday announced that its antibody treatment had fallen short in late-stage clinical trials testing its ability to prevent symptomatic Covid-19 among people recently exposed to the coronavirus. According to the company, in a trial of 1,121 recently exposed participants, those who received a single dose of AstraZeneca's antibody treatment, AZD7442, were 33% less likely to develop symptomatic Covid-19 than those who received a placebo—a difference that fell short of statistical significance. However, a parallel analysis of the data looked at a subgroup of the participants who tested negative for a the coronavirus via a nasal swab taken at the time they received the antibody treatment—and among those participants, those who received the antibody treatment were 73% less likely to develop symptomatic Covid-19. The findings suggest that the antibody treatment may help "reduce the chances of illness from potential infection in the first place," the Wall Street Journal reports (Strasburg, Wall Street Journal, 6/15; Lonas, The Hill, 6/15).

• CDC on June 14 launched the interactive Covid-19 Viral Testing Tool to help providers and patients assess Covid-19 testing options. The tool asks users to answer a series of questions to assess whether they should get tested for the virus, what type of test they should take, how to interpret any test results they receive, and their next steps for care. According to Becker's Hospital Review, the tool was launched alongside new testing guidance from CDC, including new guidelines on antigen testing (Bean, Becker's Hospital Review, 6/16).

• A third dose of a Covid-19 vaccine may bolster protection for people who have weakened immune systems, according to a small new study in the Annals of Internal Medicine. For the study, researchers gave an additional dose of a Covid-19 vaccine to 30 organ transplant patients, all of whom—despite being fully vaccinated—had either very low levels or no levels of antibodies to the coronavirus. The researchers found that, two weeks later, eight of the 24 patients who previously had no antibodies developed at least some antibodies, while the remaining six patients who had had only very low levels of antibodies got a significant antibody boost. "To me the main message here for transplant patients and immunosuppressed patients is a message of hope," Dorry Segev, a study author and associate vice chair for research and professor of surgery at Johns Hopkins University, said of the study (Syal/Edwards, NBC, 6/14; AP/Modern Healthcare, 6/14).

• The Biden administration this week agreed to purchase an additional 200 million doses of Moderna's Covid-19 vaccine, with delivery scheduled to start in the fall and continue through early 2022. According to the New York Times, the doses are intended to bolster supplies in case booster shots are needed and to vaccinate children ages 12 and under if FDA authorizes the vaccine for that age group. The purchase brings the Unites States' total acquisition of Moderna Covid-19 vaccine to 500 million doses (Stolberg, New York Times, 6/16).

• A new study published in Alzheimer's Research & Therapy found that while there is not enough evidence to show the coronavirus directly infects the brain, there is evidence suggesting potential links between the virus and two key indications for Alzheimer's: neuroinflammation and brain microvascular injury. "We discovered that SARS-CoV-2 infection significantly altered Alzheimer's markers implicated in [brain] inflammation and that certain viral entry factors are highly expressed in cells in the blood-brain barrier," Feixiong Cheng, lead study author and assistant staff at Cleveland Clinic's Genomic Medicine Institute, said. "These findings indicate that the virus may impact several genes or pathways involved in neuroinflammation and brain microvascular injury, which could lead to Alzheimer's disease-like cognitive impairment" (Carbajol, Becker's Hospital Review, 6/11).

• Widespread Covid-19 vaccination among adults can help provide protection for people who are unvaccinated—including younger populations who are not yet be eligible for vaccination, according to a new study in Nature Medicine. For the study, researchers in Israel—which until recently was vaccinating only people older than 15—assessed the vaccination records and virus test results recorded in anonymized EHRs between December 2020 and March 2021 for people older and younger than 15. They found that the more adults were vaccinated in any given community, the fewer children in that community tested positive for the virus (Anthes, New York Times, 6/10).

• FDA on June 15 announced it had approved a third batch of Johnson & Johnson (J&J) vaccines manufactured at Emergent BioSolutions' plant in Baltimore to be distributed for use, bringing the overall total of J&J doses approved for use from that plant to about 25 million. FDA earlier this month ordered J&J to throw away about 60 million doses made at the plant, citing potential contamination. However, the agency said after reviewing the plant, three batches of J&J doses have been deemed suitable for use, although Emergent is still not approved as an authorized manufacturing plant. FDA still has to review about 100 more vaccine doses from both J&J and AstraZeneca made at the plant, Becker's Hospital Review reports (Anderson, Becker's Hospital Review, 6/16).

• The coronavirus may have infected people in the United States as early as December 2019, several weeks before the nation recorded its first official case, according to a new NIH study published in Clinical Infectious Diseases. According to the study, nine volunteers who donated blood between January 2, 2020, and March 18, 2020, for an NIH study unrelated to the pandemic tested positive for coronavirus antibodies, including seven people who donated blood in five states before those states documented their first official cases of the coronavirus (Achenbach, Washington Post, 6/15; Roy, Reuters, 6/15).