Highly Vaccinated State Had Far Lower Excess Death Rates: Study

Lorraine L. Janeczko, MPH

September 06, 2022

In spring 2022, more people than expected were dying from all causes in many states, but not in highly-vaccinated Massachusetts, according to a recent research letter in The Lancet Infectious Diseases.

Dr Jeremy Samuel Faust

"In spring 2022, Massachusetts' all-cause mortality rate (deaths from all causes per 100,000 persons in a given time period) was as low as the state's rates before the COVID-19 pandemic," lead study author Jeremy Samuel Faust, MD, MS, MA, emergency physician at Brigham and Women's Hospital in Boston, told Medscape Medical News.

"Despite the substantial wave of new COVID-19 cases during that period, the state did not experience excess all-cause mortality (more deaths from all causes than would be predicted in a normal period)," he said. "That was good news."

One of Most Highly Vaccinated States

By January 27, 2022, 95% of Massachusetts's population had received at least one dose of a COVID-19 vaccine, and over 76% were fully vaccinated (defined as two doses of either the Pfizer or Moderna vaccine or one dose of the Johnson & Johnson vaccine). The average in the Unites States at the same time was about 64% of the population, according to the Centers for Disease Control and Prevention (CDC).

"We'd boosted many high-risk people in fall 2021, before Omicron swept through the state. So by spring 2022, the state's high vaccination rate, and the immunity from recent infections, limited the disease's ability to spread (provided a high level of protective immunity against death)," Faust said.

New Cases, but Not More Deaths

Throughout the pandemic, excess deaths accompanied COVID-19 outbreaks in Massachusetts, according to the CDC. But that changed after February 2022, when the reported number of COVID-19–linked deaths dropped during the spring wave of infections that was mainly due to Omicron subvariants.

To investigate this uncoupling of excess deaths from infections, Faust and his colleagues used the Massachusetts Registry of Vital Records and Statistics (MRVRS) to analyze population data from 2014 through 2019 and weekly mortality data from January 2015 through February 2020. They also analyzed case, wastewater, and hospitalization data from publicly available databases.

They used moving averages to project weekly numbers of deaths that would be expected between early February 2020 and late June 2022, and summed age-specific mortality to create state-level estimates and corrected for the smaller-than-expected state population owing to excess pandemic deaths.

Excess Deaths Dropped

Between late February 2022 and the end of the study period in late June 2022, the Omicron subvariants BA.2, BA.2.12.1, BA.4, and BA.5 became prevalent in Massachusetts and neighboring states. Within the state, at least 226,857 new cases were recorded, SARS-CoV-2 wastewater levels spiked, and COVID-19–related hospitalizations continued.

  • Despite these factors, all-cause mortality during this period was similar to pre-pandemic rates. Only 0.1 excess deaths per 100,000 person-weeks occurred — 134 excess deaths statewide — a statistically nonsignificant change (95% CI, -921 to 1189).

  • The decrease represented a 97.3% drop in excess mortality from the initial Omicron (B.1.1.529) wave that had run from late December 2021 through late February 2022 and had been accompanied by 4.0 excess deaths per 100,000 person-weeks — 2239 excess deaths statewide (95% CI, 1746-2733).

  • The decrease also represented a 92.7% drop in excess mortality from the combined Delta (B.1.617.2) and Delta-to-Omicron transition periods that had run from late June through late December 2021 and had been accompanied by 1.5 excess deaths per 100,000 person-weeks — 2643 excess deaths statewide (95% CI, 1192-4094).

"All-cause mortality is one of the most unbiased ways to analyze the effects of the pandemic," Faust explained. "Death certificates can over- or under-count COVID deaths, but all-cause mortality does not depend on cause-of-death determinations. So excess all-cause mortality tells us that, for sure, the overall situation is bad. Lack of excess mortality tells us that the situation is improving somewhat."

However, that does not minimize the threat that COVID presented to the state. "We need to ask whether other outcomes, including hospitalizations, are still occurring. Unfortunately, the answer remains yes. Keeping people, especially those at very high risk, up to date on vaccinations is extremely important to protect them from COVID and to ensure that hospitals have the capacity to treat them if needed," he advised.

Faust noted that the strength of the study is its unbiased look at mortality during recent waves of the pandemic.

"Instead of reporting COVID deaths (which can be over- or under-counted), we determined how many people would be expected to die during that time period, then we compared that number with how many actually died," he said.

"Elegant Study"

William Schaffner, MD, professor of preventive medicine in the Department of Health Policy, at Vanderbilt University Medical Center in Nashville, Tennessee, called this "a solid study" that reinforces data in the literature that show that COVID-19 vaccine protects against severe disease.

Dr William Schaffner

"Having statewide data demonstrating the protection provided by widespread acceptance of COVID vaccination is important," he said. "It is hoped that these data will provide further impetus to improve COVID vaccination efforts in under-vaccinated states."

Mary G. Krauland, PhD, research assistant professor at the University of Pittsburgh School of Public Health, told Medscape Medical News that these results "should not surprise anyone who has been watching the trajectory of cases and deaths over the pandemic timespan."

Dr Mary Krauland

"The difference between the observed and expected all-cause mortality that was noticeable even during the initial Omicron wave is consistent with the pandemic's movement from the acute phase into the endemic phase," she said.

And serious threats still remain.

"Duration and strength of immunity, as well as impact of inevitable new variants, remain uncertain," Krauland cautioned. "Clinicians still need to consider COVID-19 to be dangerous for their sickest patients."

Janet A. Jokela, MD, MPH, clinical professor and interim executive associate dean of the Carle Illinois College of Medicine at the University of Illinois Urbana-Champaign, called this "an elegant study with much-welcomed results."

Dr Janet Jokela

"Now that most tests are performed at home and not reported, and many people simply are not testing, collecting accurate data on infections remains a challenge," she told Medscape Medical News.

"The pandemic continues to impact the population in multifaceted, complex ways we do not yet understand," Jokela added. "As the authors write, further monitoring of this fluid, evolving situation is warranted." 

For Faust, "The question now is how temporary protective immunity might be."

He and his colleagues are preparing a study that examines excess mortality over the course of the pandemic nationwide.

The study received no direct funding. One co-author reports relevant financial relationships. Faust, as well as Schaffner, Krauland , and Jokela, who were not involved in the study, reported no relevant financial relationships. All experts commented by email.

The Lancet Infectious Diseases. Published online August 22, 2022. Study; supplement

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