The uncoupling of all-cause excess mortality from Covid-19 cases and associated hospitalizations in late winter and spring of 2022 in a highly vaccinated state

Abstract

Introduction: Since March 2020, all-cause excess mortality (the number of all-cause deaths exceeding the baseline number of expected deaths) has been observed in waves coinciding with Covid-19 outbreaks in the United States. We recently described high levels of excess mortality in Massachusetts during the initial 8-week Omicron wave. However, whether excess mortality continued after that period (during which an outbreak of Omicron subvariants occurred) is unknown. Methods: We applied seasonal autoregressive integrated moving averages to five years of pre-pandemic data provided by the Massachusetts Registry of Vital Records and Statistics (MRVRS) to project the weekly populations and expected deaths for the pandemic period. Observed deaths during the pandemic were also provided by MRVRS and are >99% complete for all study weeks. Results: During the 18-week Omicron subvariant period (the week ending February 27, 2022, through June 26, 2022) the incidence of all-cause excess mortality was 0.1 per 100,000-person weeks, corresponding to 148 excess deaths (95%. CI -907 to 1153), representing a 97.1% decrease from the initial Omicron period (during which all-cause excess mortality was 4.0 per 100,000-person-weeks), and a 91.9% reduction from the Delta and Delta-Omicron transition period (during which all-cause excess mortality was 1.5 per 100,000-person-weeks), despite >226,000 reported new Covid-19 cases during the subvariant/spring period. However, Covid-19-associated hospitalizations were observed during the subvariant/spring 2022 period. Conclusion: In a highly vaccinated state with a recent wave of SARS-CoV-2, all-cause excess mortality was uncoupled from new case counts, indicating the possibility of temporary protection from the most severe outcomes related to Covid-19 among high-risk individuals. However, given the possibility of waning immunity and the emerging of new variants, continued monitoring is warranted.

Age-Specific All-Cause Mortality Disparities by Race and Ethnicity During the COVID-19 Pandemic

“…To measure pandemic-associated mortality by race/ethnicity, we adapted established methods for computing age-adjusted rates, estimating excess mortality and years of potential life lost. 1,[5][6][7][8][9][10] Using the CDC Single Race designations, we divided the US population into seven race/ethnicity groups: Non-Hispanic American Indian/Alaska Native (AI/AN), Non-Hispanic Asian (Asian), Non-Hispanic-Black or African American (Black), Hispanic of all races (Hispanic), Non-Hispanic Native Hawaiian or Other Pacific Islander (NHPI), and Non-Hispanic White (White). Persons who reported "more than one race" were included for completeness but not analyzed as a group.…”

“…12 Analyses Excess Mortality Excess mortality was defined as the number of raw, observed, deaths minus modeled expected deaths. 9,10 To estimate expected deaths, we used seasonal, autoregressive integrated moving averages (ARIMA) for all-cause mortality by component demographic (race/ethnicity and age grouping). For each demographic, ARIMA models were trained using pre-pandemic population data (2014-2020) to estimate yearly populations for 2021-2023 (estimated yearly changes were divided evenly over 12 months).…”

Two years of COVID-19: Excess mortality by age, region, gender, and race/ethnicity in the United States during the COVID-19 pandemic, March 1, 2020, through February 28, 2022

“…We further adjusted (i.e., lowered) the population during the pandemic period to in proportion to the cumulative excess mortality recorded during the pandemic, so as to capture the smaller than expected population, owing to pandemic-associated all-cause excess mortality, as described previously. [7][8][9] Excess Mortality Excess mortality is defined as the difference between the number of observed and expected deaths.…”