A study published in The Lancet Global Health estimates that about 22 percent of the world's population is at risk for severe COVID-19 because of underlying illnesses and that 4 percent could require hospitalization.
The group of international researchers modeled risk using prevalence data from the Global Burden of Diseases, Injuries, and Risk Factors Study 2017 and from 2020 United Nations population estimates to determine that 1.7 billion people in 188 countries have at least one underlying disease that puts them at high risk for severe COVID-19 (range, less than 5 percent of those younger than 20 years to more than 70 percent of those 70 years and older).
If infected, about 349 million people, or about 4 percent of the world's population, could be at high risk and require hospitalization (range, less than 1 percent of those younger than 20 years to 19 percent of those 70 years and older). About 6 percent of males and 3 percent of females are at high risk, according to the study.
These estimates do not include people aged 70 and older without underlying illnesses, who are independently at elevated risk because of age. Including them would increase the global at-risk population to 24 percent, the authors said. Chronic diseases affect about 10 percent of people by age 25, 33 percent by age 50, and 66 percent by age 70 and affect males and females equally, the study found. About 23 percent of people in the world's working population (aged 15 to 64 years) have at least one comorbidity – particularly chronic kidney disease or diabetes.
Of the 1.7 billion people at increased risk for severe coronavirus disease, 0.4 billion (6 percent) have two or more underlying illnesses relevant to COVID-19 outcomes, many of them living in regions with high proportions of older people (e.g., Europe, North America).
