Levels of antibodies against SARS-CoV-2, the virus that causes COVID-19, dropped dramatically over the first 3 months of infection in 34 people recovered from mild illness, University of California at Los Angeles researchers have found.Their research letter, published yesterday in the New England Journal of Medicine, said that antibody levels against the novel coronavirus decreased by about half every 73 days and, if that rate were sustained, would be depleted within about a year.Mounting evidence of fleeting immune response In the first known estimation of the rate of SARS-CoV-2 antibody decay, the researchers studied the blood samples of 20 women and 14 men who had recovered from a mild case of COVID-19.