Most COVID-19 outbreaks in nursing homes in second half of 2021 linked to delta variant
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COVID-19 outbreaks in nursing homes throughout the last 6 months of 2021 were largely caused by the delta variant, although researchers found that COVID-19 vaccination offered significant protection against infection and death to residents.
“In June 2021, B.1.617.2 (delta) emerged as the predominant variant of SARS-CoV-2 in the United States,” W. Wyatt Wilson, MD, of the CDC’s Prevention and Response Branch, Division of Healthcare Quality Promotion, told Healio.
SARS-CoV-2 infections among nursing home residents who had completed a primary COVID-19 vaccination series had increased since emergence of the delta variant, he said.
“To characterize SARS-CoV-2 outbreaks involving nursing home residents during the delta-predominant phase of the COVID-19 pandemic, CDC partnered with 13 health departments to prospectively monitor data from 2,348 nursing homes to identify outbreaks involving three or more infected residents who had completed a primary COVID-19 vaccination series,” Wyatt said.
Participating health departments collected outbreak, facility and resident information from nursing homes with outbreaks that had three or more infections within a 14-day period among residents who were fully vaccinated.
Researchers then collected resident census data stratified by vaccination status — fully vaccinated with a primary series plus an additional dose (booster or third vaccine dose), fully vaccinated with a primary series, partially vaccinated with a primary series or unvaccinated — as well as, onset and completion date, and whether the initial infection was detected in a staff member or resident.
The investigation demonstrated that among outbreaks in nursing homes across 13 U.S. jurisdictions from July to November 2021, 98% involved the delta variant. The researchers found that among outbreaks that ended by Nov. 30, residents who had completed a primary COVID-19 vaccination series had a 28% lower risk of infection compared with residents who were unvaccinated.
They also determined that infected residents who completed a primary COVID-19 vaccination series had approximately half the risk for all-cause hospitalization (43%) and death (47%) compared with those who were unvaccinated, despite still being part of a population who is particularly vulnerable to severe infection.
“COVID-19 vaccination conferred significant protection against infection among nursing home residents and was associated with protection against all-cause hospitalization as well as all-cause death among infected residents during the delta-predominant phase of the COVID-19 pandemic,” Wilson said.
“It is critical that all eligible nursing home residents as well as staff and visitors stay up to date with CDC recommended COVID-19 vaccination series, which as of September 2022, includes receipt of an updated (bivalent) booster to maximize protection against COVID-19,” he said.
Wilson added that continued nursing home surveillance efforts are important in order to understand newer variants with enhanced transmission potential — such as omicron — and how vaccine booster doses affect the risk for infection and severe outcomes.
Wilson WW, et al. Infect Control Hosp Epidemiol. 2023;doi:10.1017/ice.2022.123.
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