How much ‘normal’ risk does Covid represent?

An article by Nick Triggle on BBC Online raises the issue of whether many deaths from COVID-19 would have occurred anyway as part of the ‘normal’ risks faced by people, particularly the elderly and those with chronic health problems who are the main victims of COVID. To provide some background, I’ve had a look at how much ‘normal’ risk COVID seems to represent.

It’s always useful to remember that we’re all going to die sometime, and the rate at which we do so is faithfully recorded in the life tables provided by the Office For National Statistics.

These provide annual ‘hazards’ — that is the proportion of people of each year of age, who do not reach their next birthday. These are plotted below on a logarithmic scale, showing an early peak due to congenital diseases and birth trauma, then a minimum around age 9 or 10 (nobody in the history of humanity has been as safe as a contemporary primary school child), and then a steady increase which is remarkably linear, apart from a sad bump in late teens and early 20’s, whose cause is all too clear. This linearity on a logarithmic scale corresponds to exponential increase— the proportion of people dying each year increases at about 9%, regardless of age. So average risk of death doubles in 8 years.

Annual risk of death (hazard) for England and Wales, 2016–2018, from Office for National Statistics.

The recent report by researchers from Imperial College London provided estimates of the age-specific risks of dying following infection with coronavirus — these are shown in the Table below.

Mortality rates following Covid-19 infection for different age groups, estimated by researchers at Imperial College London

These can be superimposed on the background mortality to produce the fgure below— they are plotted at year 7 of the decade as this more accurately represents the age at which this risk, averaged over the whole decade, pertains. The agreement is remarkable, showing the Covid risk follows a similar pattern as the background risk.

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