22 per cent of the world's population,1.7 billion people, are at increased risk of "severe COVID-19" if they're infected with the virus as a result of having at least one underlying health condition, according to a new study published in the Lancet Global Health journal that uses data from 188 countries.
Dr Andrew Clark, with the London School of Tropical Hygiene and Medicine, explains the significance and limitations of this modelling study which he co-authored and which suggests that the increased risk for many may be relatively modest.
Sputnik: Explain the significance of your findings for the average person.
Dr Andrew Clark: To understand the best way to protect those at increased risk, you first need to know how many there are. Our estimates are not exhaustive (e.g. they focus on chronic clinical conditions and exclude several risk factors) but provide a starting point for thinking about the minimum number of people that might require more stringent social distancing measures and vaccination if available.
Sputnik: What precisely do you mean by "severe COVID-19"?
Dr Andrew Clark: Severe disease is defined by WHO as "a patient with severe acute respiratory illness (fever and at least one sign/symptom of respiratory disease, e.g., cough, shortness of breath; AND requiring hospitalization)".
Sputnik: People can be at "increased risk" of something whilst remaining at low risk overall. How much of an increased risk are we talking about, in terms of people with underlying conditions developing "severe" COVID-19?
Dr Andrew Clark: To aid interpretation of the degree of risk among individuals at increased risk, we also estimated the number of individuals at high risk, defined as those that would require hospital admission if infected, calculated using previously estimated age-specific infection–hospitalisation ratios (IHRs) for COVID-19. Globally we estimate that 22% are at increased risk but only 4% are at high risk. It is also really important to consider how these risks vary by age.
Sputnik: Are certain socio-economic or ethnic groups shown to be more vulnerable than others to COVID-19, as a result of this work?
Dr Andrew Clark: Not as a result of this work. We focused on chronic clinical underlying conditions and not other risk factors (of which there are many). Adding other risk factors would be ideal but requires age/sex/country specific estimates of the population that would be affected by each of those risk factors, as well as data on how they interact/overlap with each other and with underlying conditions.
Sputnik: How certain are your figures? Is enough really known about COVID-19 to make these declarations?
Dr Andrew Clark: We say up-front (in the abstract) that our estimates are uncertain. We provide uncertainty intervals to provide a sense of that too. However, we think they should provide useful starting points for designing possible shielding or vaccination policies.
Sputnik: What policy changes or recommendations might you make based on these results?
Dr Andrew Clark: Our analysis is really trying to lay some foundations (estimates of numbers at risk by age/sex/country) on which policies could then be designed. Experts in behavioural science and policy would be best placed to design those measures and make sure they are tailored to the country of interest.
