The global effect of COVID-19 is enormous, and the havoc wrought is ongoing. Measuring the effect of COVID-19 on mortality is challenging, and analyses based on adjusted excess deaths suggest that mortality might be underestimated by the reported COVID-19 deaths.

Regardless, there have been millions of COVID-19 related deaths globally and it might be years before we fully understand the scale of COVID-19 related morbidity and mortality. From the start of the pandemic, the question of who is most at risk of severe COVID-19 outcomes, and therefore who should be prioritised for vaccination and other risk reduction measures, has been important. Relatively early in the pandemic, the OpenSAFELY analysis of approximately 11 000 COVID-19 related deaths in more than 17 million UK adults, identified several factors associated with an increased risk of death, including being male, older age, Black and South Asian ethnicity, socioeconomic deprivation, and several comorbidities (eg, diabetes, severe asthma, haematological cancers, and immunosuppression post-transplant).