Herd Immunity Revisited – an update

Herd Immunity Revisited – an update

There have been a number of responses to my previous post, most of which have missed the point. Perhaps I didn’t put it clearly enough. So let’s try to clarify it.

The main point is that I am definitely not advocating withdrawal of any attempt to control the epidemic and relying solely on the development of natural herd immunity. It is highly probable that this would lead to hospitals being stretched beyond breaking point (remembering that the policy of this and previous Tory governments in systematically reducing the ability of the NHS to cope with unforeseen crises has played a major part). I say ‘highly probable’, because nothing is certain when it comes to COVID – I suspect the virus has more tricks up its sleeve yet.

I should also say that I am in no way associating myself with the so-called ‘Great Barrington declaration’. At the same time. it does not make sense to automatically reject everything someone says simply because that person has, or is associated with, some unsavoury political views. If Mussolini made the trains run on time (whether that’s true or not), that doesn’t make it a bad idea. Nor does it mean that anyone advocating railway punctuality must be a fascist.

My central point is that lockdown and test-and-trace procedures will not by themselves permanently eradicate the virus. Textbook models of epidemics say that if you get R below 1 and keep it there, the disease will disappear. But one of the central assumptions of that model is that you are dealing with an isolated community. In the absence of herd immunity, the population is still largely susceptible, and any movement of people risks re-introducing the infection.

New Zealand can be considered as an ‘isolated community’, and they seem to have achieved that position – but at the cost of rigorous quarantining of all entrants to the country. A few other islands have done so too. The Isle of Man is making a valiant attempt to do it. Of course Britain is an island as well. But can we consider quarantine for all who come to Britain? Not just asking them to self-isolate, but putting them all into dedicated quarantine hostels for 1-2 weeks? Can you imagine that? It would have to include those coming from Northern Ireland too, which would cause a political storm.

In my view, the real purpose of the current restrictions is, or should be, to slow down the epidemic so that the NHS can continue to cope. And it buys time in the hope that an effective vaccine will become available. In the absence of a vaccine, where will it end? If the restrictions succeed in bringing the 2nd wave under control, my guess is that we would ultimately get a 3rd wave, a 4th wave and so on, until eventually enough people have been infected and we reach the unmentionable herd immunity. In that situation, we would end up with having had the same number of cases, and (unless we get more effective treatment) the same number of deaths. Those taking decisions about the nature and extent of the lockdowns need to balance those objectives against the economic, social, and psychological costs of the lockdowns.

Jeremy Dale