In New York, London and Mumbai, there might already be substantial immunity to coronavirus
To achieve so-called herd immunity – the point at which the virus can no longer spread because there are not enough vulnerable humans – scientists have suggested that perhaps 70 per cent of a given population must be immune, through vaccination or because they survived the infection.
Now some researchers are wrestling with a hopeful possibility. In interviews with The New York Times, more than a dozen scientists said that the threshold is likely to be much lower: just 50 per cent, perhaps even less. If that’s true, then it may be possible to turn back the coronavirus more quickly than once thought.