By Dr Ami Banerjee
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21 Oct, 2020
In his seminal paper, “Sick individuals and sick populations” , the epidemiologist, Geoffrey Rose, famously said, “The corresponding strategies in control are the ‘high-risk ’ approach, which seeks to protect susceptible individuals, and the population approach, which seeks to control the causes of incidence.” Two camps have emerged in the policy debate, which broadly follow Rose’s different approaches with respect to coronavirus (COVID-19), with two opposing public statements. The Great Barrington Declaration , which is broadly anti-lockdown and pro-“herd immunity”, believes that only “high-risk” groups should be shielded and the rest of society should resume normal life. The John Snow Memorandum (which I have signed) believes the only scientific response is to suppress COVID-19 at population level in order to avoid a cycle of repeated lockdowns. This week, the Lancet editor, Richard Horton states, “ On some of the most important measures of health, the four nations of the United Kingdom perform worse than our nearest neighbours. Even with coronavirus out of the picture, Britain is the sick man, woman and child of Europe.” He quoted our work, published in the Lancet in May, which showed that the at-risk population for mortality was much larger than the 1.5 million who were shielded during lockdown. We know that countries that have acted quickly and had stringent measures have had lower rates of excess COVID-19 deaths. Early on, the WHO gave a clear steer that test, trace and isolate was the way to tackle the pandemic, and we know that such systems need to be functioning well to keep the spread of the virus down. The indirect effects of COVID-19, whether on cancer , cardiovascular disease or obesity are expected to be greater if the infection rate is high, so the choice is not between economy and public health, or between cancer services and keeping infection rates down. The herd immunity camp ignores the fact that high infection rate will give the worst of all worlds. Horton is arguing that both COVID and non-COVID care are reliant on population approaches where the UK is struggling. “Low risk” individuals can become “high risk” in terms of becoming infected and spreading the infection. 10% of people are responsible for 80% of transmission. Moreover, in our study (preprint, not yet peer reviewed) in 201 individuals with persistent symptoms a median of 4 months after initial symptoms of COVID-19, we found evidence from whole body MRI scans to suggest high symptom burden and mild impairment in single and multiple organs in 66% and 25% respectively. The cohort had a mean age of 44, and was low risk in terms of risk factors (hypertension: 6%; diabetes: 2%; heart disease: 4%) and hospitalisation with COVID-19 (18%). These are preliminary data and we will be following up over time. As the debate continues and the science emerges about the exact definition and natural history of long COVID, we can agree that SARS-CoV-2 infection may have long-term consequences, even in individuals at low risk of mortality. Herd immunity rests on the idea that most people have low risk with respect to COVID-19. That may be the case with respect to deaths ( where 95% have occurred in those who are >70 years or with underlying conditions ), but may not hold true in terms of risk of infection or longer-term morbidity. If we are not sure about who is actually low or minimal risk, or rather very few people are at low risk, the population approach is the only one that the science supports and that we can sensibly follow.