Isn't this a bit of promising news, means herd immunity is probably much deeper and larger than we are currently aware.
https://www.who.int/news-room/commentaries/detail/immunity-p...
Herd immunity doesn't require perfect immunity or a 100% guarantee of it. No reasonable expert doubts that herd immunity is possible, although some argue it's too costly.
> As of 24 April 2020, no study has evaluated whether the presence of antibodies to SARS-CoV-2 confers immunity to subsequent infection by this virus in humans.
The most likely thing is that it does mean immunity, but the WHO isn't going to say that without clear evidence.
[1] https://thehill.com/changing-america/well-being/prevention-c...