In a new study, researchers found that about 1.7 billion people, 22% of the world population, have at least one underlying health condition that could increase their risk of severe COVID-19 if infected.
In addition, 4% of the world’s population (349 million of 7.8 billion people) would require hospitalization if infected.
This suggests that the increased risk of severe COVID-19 could be quite modest for many with underlying conditions.
Although the estimates provide an idea of the number of people governments should prioritize for protective measures, not all individuals with these conditions would go on to develop severe symptoms if infected.
The research was conducted by a team at the London School of Hygiene & Tropical Medicine.
As countries move out of lockdown, governments are looking for ways to protect the most vulnerable from a virus that is still circulating.
The team based their estimates on disease prevalence data from the Global Burden of Diseases, Injuries and Risk Factors Study (GBD) 2017, UN population estimates for 2020, and the list of underlying health conditions relevant to COVID-19, as defined by current guidelines.
They analyzed the number of people with an underlying condition by age group, sex, and country for 188 countries.
The researchers estimated that 349 million people worldwide are at high risk of severe COVID-19, meaning they would require hospital treatment if infected.
This risk varies from less than 1% of people under 20 to nearly 20% of those aged 70 or older, rising to more than 25% in males over 70.
In all age groups under 65, around twice the number of men as women would require hospitalization.
Above 65 years, the ratio becomes less marked because women are over-represented in older age groups due to longer life expectancy.
The researchers hope their estimates will provide useful starting points for designing measures to protect those at increased risk of severe disease.
This might involve advising people with underlying conditions to adopt social distancing measures appropriate to their level of risk, or prioritizing them for vaccination in the future.
Guidelines published by the WHO and by public health agencies in the UK and USA identify risk factors for severe COVID-19, including heart disease, chronic kidney disease, diabetes, and chronic respiratory disease.
The new study provides global, regional, and national estimates for the number of people with underlying health conditions.
The team caution that they focused on underlying chronic conditions and didn’t include other possible risk factors for COVID-19 that are not yet included in all guidelines, such as ethnicity and socioeconomic deprivation.
One author of the study is Associate Professor Andrew Clark from the London School of Hygiene & Tropical Medicine.
The study is published in The Lancet Global Health.
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