The comments on this are missing the point so to clarify: WHO is not saying that if you’ve been infected you are just as suspetible to the virus as anyone else. They’re saying we don’t have evidence that those who get the virus have long term immunity. https://twitter.com/who/status/1253995619921821698

This might seem nit-picky but the reason for it is to advise against antibodies tests being used as a sign someone is “immune.” We don’t know enough about how many antibodies one needs for immunity nor how long that immunity lasts to use these tests as a safety golden standard

Ideally, once we have more research, we will find that immunity is given after you have a certain amount of antibodies and well also know how long that immunity lasts. But until then, banking on these tests as a personal armor when one person has few antibodies and

Another might have a ton of antibodies just really isn’t a good scientific standard. You can not compare wrist guards with bullet proof armor as the same levels of protection (to vastly simplify)

TLDR: this does not say getting the virus doesn’t combat any immunity only that we don’t have enough research to use previous infection as a gold standard of lifetime immunity. Not knowing is not the same as something not being true. The idea here is caution not despair.

Also covid-19 would not be the first virus to do this: flu which is another RNA virus works similarly. If you get the flu you do have immunity to the strain for a time but that immunity wears off in 6 months which is why we get a flu shot yearly (along with the amount of strains)