The benefit in terms of estimated lives saved
Suppose that a group of people who each had expected quality-adjusted remaining years of life of 5 years, and who might have died with the virus, has been spared that because of government restrictions (“the lockdown”). We will assume that the benefit of the restrictions that prevented such deaths are the value of 5 quality-adjusted years of life multiplied by the number of lives saved. The NICE £30,000 threshold is an assessment of the (maximum) resource cost that would be justified for the UK health service to make an expected saving of one quality-adjusted year of life. To save 5 QALY would be worth up to £150,000.
We apply this figure of £150,000 (or a figure of £300,000 if we make no adjustment for co-morbidities and take 10 life years lost per death) to estimates of the possible number of lives saved as a result of lockdowns to give an overall benefit number. We compare that aggregate number with an estimate of the lost resources from the lockdown. As noted above there is no single, reliable estimate of lives that have been saved by the UK lockdown and nor is there a widely accepted single figure for the comprehensive overall cost of the lockdown (which should include lost and damaged lives into the future as a result of severe restrictions and not just lost incomes in 2020). So we present a range of estimated costs and benefits based on a wide range of assumptions that we think encompass plausible upper and lower limits on both costs and benefits.
At the high end of estimated lives saved is the difference between the projected deaths from the study of Professors Ferguson’s group at Imperial assuming no change in behaviour (500,000) (1) less an estimate of excess UK deaths (approximately 60,000 by June 2020). This 440,000 net lives saved number is likely to be a significant overestimate of likely lives saved. As noted above it does not account for changes in behaviour that would have occurred without the government lockdown; it does not count future higher deaths from side effects of the lockdown (extra cancer deaths for example); it does not allow for the fact that some of those “saved” deaths may just have been postponed because when restrictions are eased. In the absence of a vaccine or of widespread immunity, deaths may pick up again. (If the epidemic is dying out anyway those deaths will not come as the lockdown is eased but in this case, the 440,000 saved lives are also excessive because the lockdown may have come as a decline in infections was happening for other reasons).
At the other end of the spectrum would be estimates of net saved lives that are effectively zero. We set the lowest estimated net set lives well above that and use (rather arbitrarily) a “lowest” estimate of 20,000.
For each life saved we apply a factor of either 5 or 10 quality-adjusted extra years of life, each valued with the NICE guideline figure of £30,000 (20).