LONDON—A large English study showed the number of people with Covid-19 antibodies declined significantly over the summer, suggesting that getting the virus may not confer long-lasting immunity from future infection.

The survey of 365,000 adults in England who tested themselves at home using a finger-prick test showed the proportion of people testing positive for Covid-19 antibodies declined by 26.5% between June 20—12 weeks after the peak of infections in the country—and Sept. 28. We breakdown Trump on 60 minutes