How much of the World’s population is at an increased risk of severe COVID-19 disease?

A study published by Andrew Clark and others in The Lancet tried to answer this question.

The risk of severe COVID-19 disease is known to be higher in older individuals and those with underlying health conditions.  Understanding these numbers of individuals at an increased risk and how they vary between countries should help to inform possible strategies to shield or vaccinate those at highest risk. 

This study analysed data from the United Nations for 188 countries. 

They estimated that 1.7 billion people, that is 22% of the global population, had at least one underlying condition that put them at an increased risk of severe COVID-19 disease if infected. They went on to estimate that 349 million people, 4% of the global population, are at a higher risk of COVID-19 disease and would require hospital admission if infected. They estimated that 6% of males were at a higher risk compared with 3% of females.

The share of the population at increased risk was higher in countries with older populations, African countries with a high HIV/AIDS prevalence, and small island nations with high diabetes prevalence. The prevalence of chronic kidney disease, diabetes, cardiovascular disease and chronic respiratory disease contributed to this estimate. 

They concluded that about one in five individuals worldwide could be at an increased risk of severe COVID-19 infection, should they become infected. This was as a result of underlying health conditions, but the risk varied considerably by age. They did not focus on other risk factors such as ethnicity, socioeconomic deprivation and obesity.  They felt their results provided a starting point for considering the number of individuals that might need to be shielded or vaccinated as the global pandemic spreads.