‘Covid age’ model helps determine virus risk, say researchers

Experts in occupational medicine have developed a risk assessment tool to evaluate an individual’s vulnerability to Covid-19, based on their age and other risk factors

Using the model gives an individual a “Covid age”, which considers their actual age and adds additional years based on medical conditions, sex and ethnicity. For example, BAME people and females face a higher risk of Covid-19 fatality or serious illness.

Their paper published by the Occupational Medicine journal says: “Covid-ages can be translated into estimated case-fatality rates. This is complicated by uncertainties about the prevalence of asymptomatic infection, but from the limited data that are available, it is estimated that a Covid-age of 47 years might correspond approximately to a case fatality rate of 2 per 1000. For each additional 10 years of age, case fatality increases by a factor of 2.8.”

For example, a 45-year-old Caucasian male with high blood pressure and well-controlled type 2 diabetes would have a Covid age of 57. This is because the researchers believe high blood pressure and well-controlled type 2 diabetes adds eight years and four years respectively to a person’s real age for the purposes of determining the risk of Covid-19 morbidity.

The researchers defined risk based on information from more than 17 million adults in England, including 5,000 Covid-19 deaths. Information from the Office for National Statistics on sex, age and ethnicity; a study of more than 16,000 Covid-19 hospital patients; and data on the number of people living with medical conditions from the Health Survey for England were also looked at.

The tool is updated as more information about the virus and its risk factors emerges.

David Coggon, a professor of occupational and environmental medicine at the University of Southampton said: “As a method of estimating personal vulnerability to Covid-19 (i.e. the risk of serious illness or death should infection occur), the Covid-age tool is an advance on what was possible at the time when shielding letters were issued.  This is because it is based on epidemiological evidence relating directly to Covid-19 that has emerged over the course of the pandemic, rather than extrapolation from past experience with other respiratory infections.

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“The tool is designed to give the best guide to an individual’s personal vulnerability to Covid-19 that is possible from the epidemiological evidence that is currently available, and it is continually updated and refined as new evidence becomes available.  It is limited by the extent of published epidemiological data.  For example, most of the risk estimates relating to comorbidities are based on averages across all adults, but we would like to see them broken down by age.  The tool should be viewed as an aid to clinical judgment, and not a replacement for it.

“The criteria for shielding were reasonable, given what was known at the time.  The epidemiological evidence that has emerged subsequently provides a basis on which to review the earlier classifications of vulnerability and extreme vulnerability, taking into account the relative importance of different determinants of risk.”