The World Health Organization issued a warning Friday about coronavirus testing, saying there’s no evidence serological tests can show whether a person has immunity or is no longer at risk of becoming reinfected.

“These antibody tests will be able to measure that level of serology presence, that level of antibodies, but that does not mean that somebody with antibodies” is immune, said Dr. Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit.

So-called serological, or antibody, tests can indicate whether a person has had Covid-19 in the past and was either asymptomatic or recovered.

More than 560,000 of the 2.1 million…