Delaying herd immunity is costing lives

The current lockdown is protecting the healthy instead of the vulnerable.

Martin Kulldorff

Climate scientists are frustrated by people who do not believe in climate change. In epidemiology, our frustration is with anti-vaxxers. Most anti-vaxxers are highly educated but still argue against vaccination. We now face a similar situation with ‘anti-herders’, who view herd immunity as a misguided optional strategy rather than a scientifically proven phenomenon that can prevent unnecessary deaths.

Because of its virulence, wide spread and the many asymptomatic cases it causes, Covid-19 cannot be contained in the long run, and so all countries will eventually reach herd immunity. To think otherwise is naive and dangerous. General lockdown strategies can reduce transmission and death counts in the short term. But this strategy cannot be considered successful until lockdowns are removed without the disease resurging.

The choice we face is stark. One option is to maintain a general lockdown for an unknown amount of time until herd immunity is reached through a future vaccine or until there is a safe and effective treatment. This must be weighed against the detrimental effects that lockdowns have on other health outcomes. The second option is to minimise the number of deaths until herd immunity is achieved through natural infection. Most places are neither preparing for the former nor considering the latter.

The question is not whether to aim for herd immunity as a strategy, because we will all eventually get there. The question is how to minimise casualties until we get there. Since Covid-19 mortality varies greatly by age, this can only be accomplished through age-specific countermeasures. We need to shield older people and other high-risk groups until they are protected by herd immunity.

Among the individuals exposed to Covid-19, people aged in their 70s have roughly twice the mortality of those in their 60s, 10 times the mortality of those in their 50s, 40 times that of those in their 40s, 100 times that of those in their 30s, and 300 times that of those in their 20s. The over-70s have a mortality that is more than 3,000 times higher than children have. For young people, the risk of death is so low that any reduced levels of mortality during the lockdown might not be due to fewer Covid-19 deaths, but due to fewer traffic accidents.

Considering these numbers, people above 60 must be better protected, while restrictions should be loosened on those below 50. Older people who are vulnerable should stay at home. Food should be delivered and they should receive no visitors. Nursing homes should be isolated together with some of the staff until other staff who have acquired immunity can take over. Younger people should go back to work and school without older coworkers and teachers at their sides.

While the appropriate magnitude of countermeasures depends on time and place as it is necessary to avoid hospital overload, the measures should still be age-dependent. This is how we can minimise the number of deaths by the time this terrible pandemic is over.

Among anti-herders, it is popular to compare the current number of Covid-19 deaths by country and as a proportion of the population. Such comparisons are misleading, as they ignore the existence of herd immunity. A country much closer to herd immunity will ultimately do better even if their current death count is somewhat higher. The key statistic is instead the number of deaths per infected. Those data are still elusive, but comparisons and strategies should not be based on misleading data just because the relevant data are unavailable.

While it is not perfect, Sweden has come closest to an age-based strategy by keeping elementary schools, stores and restaurants open, while older people are encouraged to stay at home. Stockholm may become the first place to reach herd immunity, which will protect high-risk groups better than anything else until there is a cure or vaccine.

Herd immunity arrives after a certain still unknown percentage of the population has acquired immunity. Through long-term sustainable social distancing and better hygiene, like not shaking hands, this percentage can be lowered, saving lives. Such practices should be adopted by everyone.

Social distancing that cannot be permanently sustained is a different story. Some people will eventually be infected, and for every young low-risk person avoiding infection, there will ultimately be roughly one additional high-risk older person that is infected, increasing the death count.

Anti-vaxxers do not suffer the consequences of their beliefs, as they are protected by the herd immunity generated by the rest of us. Neither will the anti-herders, many of whom can afford to isolate themselves from Covid-19 until natural herd immunity is achieved by others. It is older and working-class people that disproportionately suffer from the current approach, becoming infected and thereby indirectly protecting much lower-risk college students and young professionals who are working from home.

The current one-size-fits-all lockdown approach is leading to unnecessary deaths. Protecting older people and other high-risk groups will be logistically and politically more difficult than isolating the young by closing schools and universities. But we must change course if we want to reduce suffering and save lives.

Martin Kulldorff is a professor of medicine at Harvard Medical School.

Picture by: Getty.

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Michael Fereday

8th May 2020 at 11:44 am

I am completely blown away by people on here suggesting that ‘herd immunity’ is the wrong course of action…it is the only course of action in a free society and has, HAS, dealt with the last 3-4 corona-viruses that regularly float around our island. All these nations who are reporting low death rates will either have ‘some’ herd immunity or will suffer a huge peak in their winter seasons (and yes, all corona-viruses are seasonal after their initial outbreak). Furthermore, unless we brainwash our kids and grand-kids to accept roll-over lock-downs in the future (and they will if we abuse them like we have done already, by telling them they are killing us for wanting to live free), we have to accept in the West that longevity of life and advanced medicine will always leave us vulnerable to viruses and bacteria, even very mild ones! Think, if this virus had come along in the 50s (65.6years), we would not have even noticed it because the numbers effected would have been statistically irrelevant.


2nd May 2020 at 12:20 am

Japan, South Korea, Taiwan, Hong Kong, Singapore, Australia, New Zealand. Total population about 250 million people. Total Coronavirus deaths just over 800. And all nearer to China and affected/infected longer. Thank God they all ignore this “Herd Immunity” nonsense! Meanwhile over 3 times as many Swedes have died out of a population of just 10 million.

Imagine if the medics in Lagos in 2014 had applied “Herd Immunity” to the Ebola outbreak then. How many millions would have died in that city of 21 million people? How many billions would have died worldwide? Coronavirus will not be the last pandemic, and “Herd Immunity” could kill all humanity if applied.

Philip St. John Lewis Davies

2nd May 2020 at 3:46 pm

You speak as if there is only a stark choice available to us, in the throes of this pandemic, of either imposing a complete, indefinite Lockdown, or accepting a totally fatalistic let-nature-take-it’s-course approach. Yet the sensible answer was always to be found somewhere between these two falsely polarised positions, across a range of clinical and social possibilities. And while Ebola is uniquely horrifying in both the symptoms suffered by it’s victims and in having a 40% mortality rate among the infected, it is only spread by physical contact and can be effectively controlled by keeping the sick isolated from the general population. Also, in Ebola-rife parts of Africa so-called Lockdown was only applied to the general population in the severest affected areas of any one country, and was deliberately not pursued to the detriment of people’s livelihoods. Likewise, ‘ScienceAlert’ [see their Website] advises that ‘Until we have a vaccine, anyone talking about herd immunity as a preventative strategy for COVID-19 is simply wrong.’ I of course agree with all these clinical views. Neither were our British government and nor are the Swedish government in favour of just letting the disease take it’s course: both had in mind a suite of measures that are essentially the same. As the ‘ScienceAlert’ article goes on to say: ‘Fortunately, there are other ways of preventing infections from spreading, which all boil down to avoiding people who are sick.’ What is revealing here is the difference in the way Sweden and Britain have respectively administered that ‘avoiding people who are sick’ part of this approach, with Sweden tending towards an emphasis on the isolation of the sick away – especially – from the most vulnerable, but also in order to quarantine them away from the healthy majority of the population, while in Britain in worrying contrast we have erred in the direction of indiscriminately putting everyone – the entire country – into a non-clinical purdah: the first is a sensible and essential precaution, whereas the second is more a nervous panic-measure that is becoming increasingly counter-productive by the day. An important additional consideration is that ‘Herd Immunity’ is not achievable without unacceptably high death rates – as John Shea quite correctly believes – UNLESS that immunity can be acquired with the aid of vaccination and other clinical preventative and curative measures – a necessary qualification that he perhaps does not fully appreciate. Indeed, the only meaningful application of the term ‘herd immunity’ and the pursuit of such disease-resistance must involve medical interventions. Otherwise you are making a pointless ‘straw man’ argument against a completely reductive misunderstanding of community immunity. Because immunity by definition kills no-one, whereas a draconian yet panicky Lockdown will – and ruin the economy into the bargain. I just wish opinions didn’t so often go to extremes in modern Britain. Have we all taken leave of our senses?

David Margison

2nd May 2020 at 8:06 pm

Well said Philip


8th May 2020 at 8:24 am

I never mentioned the lockdown. The simple fact remains that several vastly and densely populous Asian city-states have kept their Coronavirus death rates below ONE death per MILLION population through relatively mild travel restrictions and testing and tracing and treatment. And they are not alone. The Sweden-vs-Britain argument is a red herring. As for vaccines, yes, I am aware of their potential, and their current complete non-existence.

David Margison

2nd May 2020 at 8:00 pm

“Thank god they all ignored herd imunity”?

Get your facts right. Japan had their first case in january, they didn’t impose a lockdown. Everything carried on as normal, schools, concerts, shopping, sports, restaurants. Only recently have they given schools a month off. They have a population of 127.5 million, with a large ageing population. They don’t have our obesity problem. The elderly are fitter than our aged population. Another factor is their cultural preference for bowing rather than shaking hands.
So no lockdown, less deaths!

Poor research is propaganda!

And in the near future I suspect all the reported figutes coming out of the far east will be discredited



8th May 2020 at 8:08 am

I got my facts right. You, on the other hand, seem not to have actually read my comment, in which I NEVER mentioned the lockdown.

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