Intended for healthcare professionals

Letters Aiming for “zero covid”

To achieve “zero covid” we need to include the controlled, careful acquisition of population (herd) immunity

BMJ 2020; 370 doi: (Published 09 September 2020) Cite this as: BMJ 2020;370:m3487
  1. Raj S Bhopal, emeritus professor of public health
  1. Edinburgh Migration, Ethnicity, and Health Research Group, Usher Institute, Medical School, University of Edinburgh, Edinburgh EH8 9AG, UK
  1. raj.bhopal{at}

Torjesen asks whether the UK should aim for zero covid.1 Of course it should, but how? My suggested strategy includes herd immunity, which I rename population immunity given the antipathy to the word herd, evoking animals.2

On 7 April 2020 Martin McKee wrote to the covid-19 global researchers email group “seeking sensible thoughts about coming out of lockdown.” I responded with an eight point plan, the last point being that in the absence of a vaccine we should allow young people under 30, particularly women, to get the infection voluntarily, preferably in controlled circumstances. This kind of approach has been conceptualised and modelled by others.345 McKee replied that it was good to think out of the box. But this is already happening in unplanned and haphazard ways.6 Letting the pandemic unfold uncontrolled is not public health strategy.2

I suggest population immunity as part of a comprehensive response.2 I estimate that about 40-50% population immunity would be sufficient to suppress an infection with a reproduction number of about 1 or slightly more, which requires continuing, reasonable control measures. Others consider this proportion to be much lower.7 Allowing infection in people at low risk is justifiable if we make it safer for them than allowing it to occur uncontrolled.2

Covid-19 is currently rarely fatal in children and young people, less so than influenza for which we already have a vaccine. Showing that a vaccine is safer than covid-19 in young people is, therefore, tough.89

Public debate, including on population immunity through both natural infection and future vaccination, is urgent.2 My paper has been covered in national and international media with huge support from public and professionals. My views have been interrogated in detailed interviews by Wired ( and Contagion (

Population immunity through a mixture of vaccination and natural infection is the only long term solution for zero covid.2


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