Using the monoclonal antibody cocktail REGEN-COV reduced the risk for symptomatic COVID-19 infection 81% in those exposed to a COVID patient, according to a New England Journal of Medicine study yesterday.The findings were used in the US Food and Drug Administration's recent decision to expand the drug's emergency-use authorization; now, it can be used as post-exposure prophylaxis in high-risk populations, not just a treatment during infection.All COVID-19 cases reduced by 66%The study included 1,505 people ages 12 and up who never had COVID-19 and who had a household member test positive within 96 hours (median age, 42.9 years).