Relying on herd immunity to beat Covid won’t work

I’ve always been sceptical about claims for building up herd immunity as a protection against Covid, and thought Sweden’s reliance on it to be misguided.

Herd immunity is usually claimed when a high proportion of the ­community has been vaccinated so that even unvaccinated people are protected. But herd immunity is ­difficult to build and we never reach it with most infections.

So, for instance, we’ve never achieved herd immunity for malaria or Ebola. It just doesn’t happen, says Professor Chris Whitty in the BMJ whose views are always worth a listen.

He thinks relying on herd immunity is wrong scientifically, practically and probably ethically as well, arguing that it’s an unpredictable tool to use.

The theory of herd immunity depends on the second assumption that immunity will be maintained.

But we don’t know this for Covid. In fact, we know the opposite – that antibodies wane quite quickly.

Even if we could achieve herd immunity, practical questions give Prof Whitty pause. Let’s say it was possible – you’d still have to identify all the people who get Covid illness then isolate them for the time that it is in circulation and a threat.

This simply couldn’t be achieved for such a highly ­infectious virus. According to Prof Whitty, SAGE, the nation’s committee of scientists who examine all Covid data, have looked at this twice and came to the same conclusion both times – it wouldn’t work. Then there’s a third reason Prof Whitty has problems with pursuing herd immunity, that it’s unethical, because it would lead to a significant number of people dying who otherwise wouldn’t have died.

Furthermore it would almost certainly lead to much greater ­pressure on the NHS and even more indirect damage because a lot of routine medical care would have to be cancelled.

Eradicating this virus is not only impractical it’s probably impossible. So far we’ve managed to eradicate only one human disease – smallpox.

The likelihood is Covid will remain in circulation, held under control by vaccination and testing, with seasonal blips but, hopefully, little serious disease.

Whitty believes it is incumbent on us to control this virus using the tools we’ve got, along with vaccines. Like him, my belief is unshakeable in “the ability of science to get us out of this hole”.

It’s doing a pretty good job already.