https://www.scientificamerican.com/article/concerns-about-waning-covid-19-immunity-are-likely-overblown/

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.