Reduction in COVID-19-related mortality over time but disparities across population subgroups

More than 3 years into the pandemic, the world has made major progress in understanding, preventing, and treating COVID-19, and has experienced periods of substantial individual and societal disruption. High rates of immunity from vaccination and recovery from previous infection are now observed among populations,¹ which are likely to attenuate the severity of new infections due to long-lasting cellular and humoral immunity.² Greater normalcy has returned as governments have ended pandemic restrictions or declared an end to COVID-19 as a public health emergency.3, 4 Despite this progress, SARS-CoV-2 continues to circulate and thousands of COVID-19-related deaths occur weekly worldwide,⁵ suggesting that there is further room for improvement.

In this issue of The Lancet Public Health, Linda Nab and colleagues⁶ report the findings of a retrospective cohort study in England that used the OpenSAFELY platform to examine COVID-19-related mortality in adults aged 18 years or older across five pandemic waves spanning almost 2·5 years. Each pandemic wave cohort included data from about 19 million adults with continuous general practice registration. COVID-19-related deaths were captured from death registry linkage and defined by citation of COVID-19 as an underlying or contributing cause of death. Crude and age-standardised and sex-standardised mortality rates and relative hazards of COVID-19-related deaths across demographic and clinical subgroups were assessed for each pandemic wave. Because of dynamic changes in public health measures, population immunity, clinical management, and transmissibility and severity of SARS-CoV-2 variants, the study could not disentangle precise contributions of individual factors but nevertheless provides valuable insights and a comprehensive picture of temporal changes.

Nab and colleagues⁶ found that COVID-19-related mortality rates decreased over time, with crude rates per 1000 person-years declining from 4·48 deaths during wave one (March 23–May 30, 2020) to 0·67 deaths during wave five (June 24–Aug 3, 2022). Compared with wave one, wave two (Sept 7, 2020–April 24, 2021), corresponding with alpha (B.1.1.7) variant circulation and before most adults were vaccinated against COVID-19, showed broad decreases in mortality rates. This might reflect the effects of early public health efforts or improved clinical management, although this should be interpreted in the context of measuring incidence of COVID-19-related deaths over periods with varying lengths and rates of SARS-CoV-2 infection. During wave three (May 28–Dec 14, 2021; in which delta [B.1.617.2] was the dominant variant), the largest decreases in mortality rates were observed among groups who were prioritised for COVID-19 vaccination, especially older adults who had very high primary vaccine series coverage. This finding is consistent with data that have shown a lower risk of severe COVID-19-related outcomes among vaccinated adults, and highlights the fundamental importance of vaccination for all adults.7, 8

Despite overall reductions in COVID-19-related mortality rates over time, improvements were not realised equally across population subgroups. Notwithstanding higher vaccine coverage and relative reductions in COVID-19-related mortality over time, older adults continued to show higher COVID-19-related mortality rates than younger adults, although this study could not discern whether COVID-19 was the primary cause of death or a contributing factor, such as by exacerbating chronic health conditions. Furthermore, in settings of high vaccine coverage, adults with conditions associated with frailty or reduced vaccine response (eg, organ transplant, haematological malignancy, or advanced kidney disease) did not show the same reductions in mortality rates as those without these conditions, suggesting that focused efforts in key population subgroups remain crucial. These efforts might include differential vaccine schedules in groups who are at high risk of severe outcomes, a low threshold for testing and early initiation of effective but underused antiviral therapies (such as nirmatrelvir–ritonavir), and implementation of non-pharmaceutical measures, such as face masks indoors in some settings and improved ventilation.⁹ The broader community should also protect people who are at high risk of severe outcomes, such as through testing and avoiding public places when unwell. Using the Index of Multiple Deprivation, the Nab and colleagues⁶ additionally found that relative mortality in populations living in the most socially deprived areas was higher than in less deprived areas. This finding corresponded with lower vaccination coverage in areas with greater deprivation and might also reflect other differences in access to or utilisation of health-care services, or more crowded living conditions. These findings underscore a need for improved outreach and COVID-19 vaccination among the most vulnerable groups in society.

Major progress has been made and we are no longer seeing the dramatic mortality rates observed during earlier COVID-19 pandemic periods. However, COVID-19 continues to kill thousands of people, and specific population subgroups have a greater burden. The study by Nab and colleagues⁶ shows the value of strong national and integrated surveillance and vaccine registry data to record the implications of the pandemic and inform public health responses. It also provides robust data on groups in whom measures to reduce severe COVID-19-related outcomes could be more effectively focused, while continuing to minimise individual and societal impacts from COVID-19.

We declare no competing interests. The views expressed here are those of the authors and do not necessarily represent the official position of the US Centers for Disease Control and Prevention.