COVID-19: Asymptomatic Infection / B.1.1.7 Variant Deadlier? / Bamlanivimab for Prevention / Mitigation Measures Through July?

By Amy Orciari Herman

Edited by Susan Sadoughi, MD, and André Sofair, MD, MPH

Catch up on some of the latest COVID-19 news:

Asymptomatic infection: Roughly one in three SARS-CoV-2 infections may be asymptomatic, according to a review in the Annals of Internal Medicine. Researchers examined data from 61 studies that used either PCR or antibody testing to determine SARS-CoV-2 infection. In four large, PCR-based studies, the proportion of people who tested positive and had no symptoms at the time of testing ranged from 43% to 77%, with a median of 46%. In addition, in 14 PCR-based studies that assessed whether asymptomatic people became symptomatic after a positive test, the proportion of infected people who remained asymptomatic ranged from 11% to 100%, with a median of 72%. Taken together, the researchers write, these data suggest that 33% of SARS-CoV-2 infections could be asymptomatic. The highest quality antibody studies, from England and Spain, also yielded an asymptomatic proportion of 33%.

B.1.1.7 variant deadlier? B.1.1.7 — the SARS-CoV-2 variant that first emerged in the U.K. and has now been detected in more than 50 countries — could be deadlier than older strains, U.K. officials warned over the weekend. They reported several data sets that suggest a mortality hazard ratio ranging from 1.3 to 1.9 with B.1.1.7 relative to other strains. One official cautioned that the data are "not yet strong," BBC News reports. He added, "I want to stress that there's a lot of uncertainty around these numbers and we need more work to get a precise handle on it." As of Friday, B.1.1.7 had been detected in over 20 U.S. states.

Bamlanivimab: The monoclonal antibody bamlanivimab may help prevent symptomatic COVID-19 among nursing home residents, the manufacturer reported late last week. Some 965 residents and staff at U.S. nursing homes who tested negative for SARS-CoV-2 were randomized to receive bamlanivimab or placebo. At 8 weeks, the risk for symptomatic COVID-19 was 57% lower with bamlanivimab. In addition, among the nursing home residents, four COVID-19–related deaths occurred — all in the placebo group. In November, the FDA granted bamlanivimab emergency use authorization as a treatment for some outpatients with mild-to-moderate COVID-19.

Mitigation measures through July? COVID-19 mitigation measures, like mask-wearing and social distancing, will need to be strengthened until late July in order to avoid millions of additional infections in the U.S. — even as more and more of the population gets vaccinated — researchers contend in the New York Times. Their modeling study made several assumptions, including that over 105 million Americans have already been infected and that the vaccines are 95% effective. They calculated that if current restrictions are in place until late July, there will be 158 million total infections by then. If restrictions are lifted in February, there will be 29 million additional infections; if they're lifted in March, there will be 6 million additional infections. If, however, restrictions are strengthened until late July, the country will avert 19 million infections. The study has not yet been peer-reviewed.