The WHO opposes such "passports" because recovery from the virus might not protect a person from reinfection.

"There is currently no evidence that people who have recovered from #COVID19 and have antibodies are protected from a second infection," the UN health body said on Twitter.

The WHO later took down the tweet the in order to clarify its message, saying: "We expect that most people who are infected with #COVID19 will develop an antibody response that will provide some level of protection... What we don't yet know is the level of protection or how long it will last."