Understanding Risk for Severe COVID-19

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Understanding Risk for Severe COVID-19

This page undergoes regular review and was last comprehensively reviewed on January 17, 2023. Some sections may reflect more recent updates.

Clinical decision-making surrounding a diagnosis of COVID-19 begins with an assessment of risk for severe outcomes such as hospitalization and critical disease related to SARS-CoV-2 infection. Risk exists on a continuum, as illustrated below.

Risk for severe outcomes is impacted by both modifiable and non-modifiable health factors which can guide patient counseling and treatment decisions. Consistently, the most important non-modifiable risk factor for severe COVID-19 outcomes is older age (particularly ≥65 years) (CDC, November 2022; Vo, October 2022; Williamson, July 2020). Accumulating medical comorbidities such as obesity, diabetes and end-organ dysfunction further increase risk.

The major modifiable factor to decrease risk is SARS-CoV-2 vaccination, particularly recent booster vaccinations, which significantly reduce likelihood of severe disease in vulnerable populations such as older adults (McConeghy, September 2022; Havers, September 2022). Additional prior antigen exposure, such as through SARS-CoV-2 infection, also appears to reduce the risk of severe disease particularly when coupled with up-to-date vaccination (see our Immunity page; Wu, February 2023; Altarawneh, March 2022).

Furthermore, a patient’s degree of immunocompromise contributes not only to an impaired ability to fend off viral infections (Roberts, October 2021), but may attenuate the response to SARS-CoV-2 vaccination and associated protection (Gong, December 2022; MacKenna, July 2022; Sun, December 2021; Boyarsky, May 2021). There may, however, be significant variation in immunoprotection against COVID-19 among individual patients with the same immunocompromising condition (see NIH Guidelines Panel, December 2022 for examples of risk stratification within certain populations).


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