PandemicPreparedness

In a journal article published in The Lancet Global Health, experts have estimated the global, regional and national populations at risk for severe COVID-19 infection. The researchers took estimates of the burden of chronic illness and medical conditions from the Global Burden of Diseases, Injuries and Risk Factors Study (GBD) 2017 and United Nations (UN) population estimates for 2020 to understand the number of people living with chronic conditions known to increase the risk of severe COVID-19 infection.

These conditions were grouped into 11 categories based on WHO reported guidelines as to conditions known to have poor outcomes with COVID-19 infection:

1. cardiovascular disease, including that caused by hypertension (high blood pressure);
2. chronic kidney disease, including chronic kidney disease caused by hypertension;
3. chronic respiratory disease;
4. chronic liver disease;
5. diabetes;
6. cancers with direct immunosuppression (like some leukaemias);
7. cancers without direct immunosuppression, but with possible immunosuppression caused by treatment (some cancer treatment suppresses the immune system);
8. HIV/AIDS;
9. tuberculosis (excluding latent infections);
10. chronic neurological disorders; and
11. sickle cell disorders.

The modellers then used the known estimates of chronic conditions by age, sex and population to estimate how many people have an increased risk at national regional and global scales. They took into consideration that a person can have more than one of these conditions and that this would not necessarily be worsened by increased age. They note that there is an association between male sex and hospitalisation and therefore considered that men were twice as likely to be at high risk across age groups.

In the results, the authors note that 1.7 billion people (22% of the global population) have at least one underlying condition that could increase their risk of severe COVID-19 infection. Importantly, this does not include the population of older people without chronic conditions noted above. Of these with increased risk, 4% overall were considered to be at high risk, defined as individuals with at least one condition who would require hospitalisation if infected.

The authors included models of each nation, with estimates of the proportion of each country considered to be at increased and high risks arranged by UN region. The models have also been tested with recent reports of COVID-19 hospitalisation rates and found to closely match the experienced rates of severe infections as seen in Sweden.

In discussion and conclusion, the authors note that although over 1 in 5 people has an increased risk globally, the degree of risk may be only a modest increase and only 1 in 20 would require hospitalisation, depending on their age. Per country models can be adjusted using the authors' Excel spreadsheet tool, made available freely here.