COVID-19 triggers a strong immune response in most people. Yet several recent studies observed that the amounts of antibodies in those recovering from the virus appear to decline within a few months of infection. The findings set off a frenzy of speculation that immunity to the virus may not last long, throwing cold water on hopes for a vaccine. Many scientists say such worries are overblown, however.
A June 18 Nature Medicine study conducted with a small group of patients in China showed that in both asymptomatic and symptomatic individuals with COVID-19, antibody levels dropped significantly during recovery—and that the levels became undetectable in 40 percent of the asymptomatic group. A preprint study by researchers in England that was posted online in mid-July similarly demonstrated that antibody levels declined substantially within a few months of infection and that people with less severe illness had fewer antibodies. And most recently, a small study, published on July 21 in the New England Journal of Medicine, found a “rapid decay” in antibodies among individuals with mild cases of COVID-19.
These results may sound universally grim. But several experts Scientific American spoke with said they thought that the declines were not as scary as initially portrayed, that some reduction in antibodies is normal and expected and that antibodies are just one piece of the immunity puzzle. Evidence from other viruses and animal studies of SARS-CoV-2 infection provide reason for optimism, they add. That assessment is no doubt reassuring for vaccine developers, some of whom are already racing ahead with large-scale clinical trials. Only longer follow-up studies of people infected with the novel coronavirus will show whether antibodies confer lasting protection, however. [Continue reading…]