How many are at increased risk of severe COVID-19 disease? Rapid global, regional and national estimates for 2020

Andrew Clark; Mark Jit; Charlotte Warren-Gash; Bruce Guthrie; Harry HX Wang; Stewart W Mercer; Colin Sanderson; Martin McKee; Christopher Troeger; Kanyin I Ong; Francesco Checchi; Pablo Perel; Sarah Joseph; Hamish P Gibbs; Amitava Banerjee; Rosalind M Eggo

We focused our analysis on the list of underlying chronic causes of disease available in GBD2017, and did not include risk factors, such as pregnancy, smoking, under-nutrition, obesity, working in the health and social care system, homelessness and general frailty e.g. individuals living in care homes and other facilities. The importance of these factors on the severity of COVID-19 is still to be determined, although some national guidelines already include frailty in decisions about treatment. 34 We found that the age threshold for older people without underlying conditions led to a substantial increase in the overall number of people that may be considered at increased risk of severe COVID-19 disease. Individuals in developing countries may be frailer than those of an equivalent age in developed countries, and there may be other societal and economic considerations. Older individuals without these underlying conditions could suffer adverse mental health consequences from long periods of isolation. However, of the approximately 1 billion individuals aged 50+ years that we estimate to be at increased risk of severe COVID-19 disease (table 1) many may not be aware of their underlying condition. 35 For example, CKD has a very high prevalence in many countries, but more than 90% of these cases are likely to be undiagnosed. 23 Age thresholds could therefore play a critical role in shielding the large number of older individuals without a diagnosis. Indeed, while our analysis quantifies numbers who could benefit from shielding, in practice the low coverage of diagnosis and treatment for many chronic conditions in low-income settings means that the age threshold could largely determine the effective target group.