The Covid-age risk assessment can calculate the risk of an individual developing serious or fatal COVID-19 and can be used to determine if an employee is safe to be at work. Four of the UK’s leading experts in occupational health medicine explain how the tool was developed, in an editorial published in Occupational Medicine journal.
The evidence-based risk model considers a person’s age and adds extra years to take into account different medical conditions, sex and ethnicity, to estimate the risk COVID-19 poses to an individual.
As the chance of death from COVID-19 increases with age, the specialists felt that an individual’s vulnerability can conveniently be expressed as the equivalent age that the person becomes once their medical conditions have been taken into account: their ‘COVID-19 age’.
The editorial is written by David Coggon, Peter Croft, Paul Cullinan and Anthony Williams, and details how specialists worked urgently in order to create the tool in order to improve on earlier advice that had been given to individuals, which was not necessarily evidence-based and which could have been incorrect.
They started out by defining risk from information contained within a report which included more than 17 million adults in England. The report included 5,000 COVID-19 deaths and assessed if risk factors were present from primary care records. They then checked the findings from this report against data from four independent sources:
- Office for National Statistics (ONS) data on mortality from COVID-19 by sex and age
- ONS estimates of coronavirus-related deaths by ethnic group
- A study of over 16,000 COVID-19 hospital patients
- Data on the number of people living with medical conditions from the Health Survey for England.
They then defined how high the risk was for different medical conditions and checked this was correct by referring to the sources listed above. As new studies have been published the risk estimates have been refined.
The authors highlight that their assessment is based on the evidence available; this could mean that rarer medical conditions are liable to statistical uncertainties. They also say that clinical judgement should be applied alongside the risk assessment, especially if data doesn’t exist for certain medical conditions.
The risk assessment is only one element of the equation and the authors advise that control measures, the prevalence of COVID-19 in the local community, an individual’s personal value judgment and governmental advice also need to be taken into account.
An advance on what was possible when shielding letters were issued
One of the editorial authors, Professor of Occupational and Environmental Medicine, David Coggon explains that given new evidence has emerged since shielding letters were sent out, it would be sensible to reassess a person’s risk.
Professor David Coggon 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.
“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.”
The editorial is available from: https://doi.org/10.1093/occmed/kqaa150
Article written by Dr Yvette Martyn