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Vaccines Bring Home the Failure of Herd Immunity

Vaccines Bring Home the Failure of Herd Immunity

Tuesday, 15 December, 2020 - 07:30

It’s time for some good news. A few hours before I wrote this, my father (who is 83 and had a nasty case of pneumonia a few years ago) phoned to tell me that he will be having his first Covid-19 vaccination shot this week, with a second to follow in the first week of January. My 81-year-old mother will get her jabs at the same time. The British rollout continues apace, just as the introduction of the same vaccine is ready to start in the US.

It’s an exciting development. After a miserable year, my parents can plan on returning to an active and happy retirement. As this fascinating chart by Deutsche Bank AG with FDA data makes clear, the Pfizer Inc. vaccine, which will be going into my parents’ arms, has no significant effect for the first week. After the second dose, the effect compared to the placebo is dramatic and undeniable.

The distributional challenges remain intense, given that this vaccine needs to be kept very cold. Beyond the logistical challenge, there are moral ones. In Britain, elderly patients who are at most risk, like my parents, will go first. In the US, with different states free to make different decisions, there is a risk of dissension. There are powerful though controversial cases to be made for giving priority to prisoners, who are at great risk; there is also a case for giving lowest priority to those who can easily work from home. And there are also arguments about international equity; as Covid knows no political boundaries, it might be “enlightened self-interest” for wealthier nations to distribute vaccine supplies to poorer countries on their borders, or to parts of the world that have particularly severe outbreaks. Such decisions would be controversial.

The past couple of months have made clear that the world needs a vaccine to put the pandemic behind us. The resurgence of the virus has done great damage to the rival theory, that “herd immunity” (where the disease runs out of new people to infect) could be reached soon by allowing it to spread in the population.

Sweden famously eschewed strict lockdowns and left its schools open. The hope was that this would bring herd immunity, so that it would avoid a second wave. That theory now looks very questionable. A chart of confirmed cases per 100,000 over the last 14 days shows that Sweden is in pale blue. It is suffering a second wave fully comparable with those of other European countries. Unlike those that locked down, its cases are still rising.

Sweden’s hospitals are at capacity, and it is drafting in help from other countries. The popular argument that it had done something uniquely clever still had much to recommend it two months ago. It is very hard to sustain now.

Put differently, another chart shows deaths per day in Sweden and neighboring Denmark. I multiplied Denmark’s number to account for its smaller population, and provided a seven-day moving average for Sweden, whose data are very noisy. Sweden endured an appalling death rate compared to Denmark’s; and it is once more suffering a worse death rate than its neighbor. There is room for argument about definitions, and Sweden’s numbers may be inflated by a particularly mild flu season last year; but the notion that it has gained from its relaxed attitude to social distancing now seems close to impossible to sustain.

This isn’t to say that debate on the merits of lockdowns has been wasted. Plainly, they have serious economic consequences, and school closures may have lasting negative consequences for children. But there was no “free lunch” to be had by letting the disease rip. The many trade-offs were, we can now see, far subtler.

It’s also fair to say that the herd immunity theory had something going for it. Places that suffered the worst outbreaks in spring have enjoyed noticeably easier times in the last two months.

Charts for New York City, blindsided by the pandemic earlier this year, show, both in terms of hospitalizations and deaths, that the current wave isn’t remotely comparable to the first.

Part of this will be due to the salutary effect of the spring outbreak, which left New Yorkers in little doubt that it was worthwhile to wear masks, and socially distance. However, they are also consistent with the notion that the first outbreak increased immunity in the population and made it harder for the virus to take hold a second time.

Whitney Tilson of Empire Financial Research, whose work on coronavirus I have recommended in the past, offered the following mea culpa in his most recent bulletin, having previously used the herd immunity theory to predict that the current waves in the US and Europe would be far less severe than the previous ones: in failing to anticipate the magnitude of the latest third wave in the US (and second wave in Europe), I made two mistakes:

Most importantly, I didn’t fully appreciate that while some hard-hit areas (northern Italy, the greater NYC area, and parts of Florida) likely reached the herd immunity threshold, the vast majority of the US and Europe did not – and hence were vulnerable to another terrible wave…

My second mistake was failing to anticipate how quickly after the earlier wave(s) most Americans and Europeans (both citizens and their governments) would become careless/complacent and, especially in the US, the politicization of this public health issue and the resulting resistance to even easy, basic things like wearing masks. As a result, the virus came roaring back…

With the numbers affected now at dreadful levels once again, and months to go before enough of us are vaccinated to take life back to normal, it would make sense if everyone carried on in a careful and socially distanced way. It won’t be fun, and it will be negative for the economy, but a few more months of slow activity should have little impact on market prices with the vaccine now available.


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