Assessing Excess Mortality from COVID-19 Across US States

Increasingly the topic of “how serious is COVID-19 anymore?” finds its way into discussions around the pandemic. As we wade into the winter months, when we’ve seen COVID-19 numbers surge, and now with most of the world fully “open” and influenza starting to bubble up again, it’s frustrating that we’re still battling questions about how devastating this disease can be.

There are several issues related to COVID-19 that we’re still trying to understand. Long-COVID for example, is one that is increasingly downplayed and yet something millions of Americans suffer from. Too often we fail to understand that infectious diseases can inflict lifelong outcomes that cause neurological, joint, and other health issues.

Another example though, is all-cause excess mortality from COVID-19 cases. Excess mortality are those deaths, regardless of cause, that exceed the baseline numbers we’d expect to see. Since the beginning of the pandemic, excess mortality has occurred and especially in relationship to surges of cases we’ve seen across the United States.

In a recent article within The Lancet Infectious Diseases, a team of researchers assessed all-cause excess mortality and sought to uncouple it from COVID-19 in US states with high vaccination rates. The authors emphasized the need to assess this due to notable decreases in deaths related to COVID-19 despite the surge of Omicron cases.

Utilizing population data and mortality data in Massachusetts, they then applied seasonal autoregressive integrated moving averages to project those weekly deaths we’d expect at such a point in the pandemic. The authors noted that during the 18-week period following Omicron variants (including BA.2, BA.4, and BA.5) becoming prevalent, there was “0·1 excess deaths per 100 000 person-weeks, corresponding to 134 excess deaths (95% CI –921 to 1189; despite at least 226 857 newly recorded cases, as evidenced by corresponding substantial spikes in SARS-CoV-2 wastewater levels and changes in testing volume.

This value corresponds to a 97·3% reduction in excess mortality compared with the 8-week initial omicron (B.1.1.529) wave, during which excess mortality was 4·0 per 100 000 person-weeks (2239 excess deaths; 95% CI 1746–2733), and a 92·7% reduction in excess mortality compared with the combined 26-week delta (B.1.617.2) and Delta-to-Omicron transition periods, during which excess mortality was 1·5 per 100 000 person-weeks (2643 excess deaths; 95% CI 1192–4094).”

Interestingly, new COVID-19 related hospitalizations continued to spike during this time, pointing to the influx of cases within the community, but also challenges of intervention efforts. The authors note though that with this finding, such hospitalizations were less severe or exacerbation of chronic medical conditions but didn’t ultimately cause proximate mortality.

In those states with high rates of vaccination, the authors emphasized that these findings point to a certain level of protection against those most severe outcomes related to COVID-19. Uncoupling of excess mortality and new COVID-19 cases, they argue, is an important metric to assess the severity illness, impact of emerging variants, and duration of protection from infection via vaccination.