"There is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection,” the United Nations agency said in an April 24 statement.

The WHO guidance came after some governments suggested that people who have antibodies to the coronavirus could be issued an "immunity passport” or "risk-free certificate” that would allow them to travel or return to work, based on the assumption that they were safe from re-infection, according to the statement. People issued such a certificate could ignore public-health guidance, increasing the risk of the disease spreading further.

While many countries are currently testing for antibodies, these studies aren’t designed to determine whether people recovered from the disease acquire immunity, the WHO said.