Two-Dose COVID-19 Vaccination Among Nursing Home Staff Waned in Benefit Against Omicron Variant

Soham Sinha, MS

Despite success against earlier waves of COVID-19, the recommended 2-dose vaccine regimen against SARS-CoV-2 infection was not associated with reduced rates of adverse outcomes among US nursing home staff and residents during the Omicron variant wave last year.

In new research of longitudinal cohort data from Medicare- and Medicaid-certified nursing homes from May 2021 -January 2022, a team of investigators from the University of Chicago reported that incidences of COVID-19 and related deaths were decreased among residents and staffs in nursing homes where staff members had greater vaccination rates prior to the Omicron variant wave. However, the correlation between staff vaccination rates—defined as 2-dose regimen completion per individual—and reduced COVID-19 infections and deaths in such facilities was lesser pronounced by the end of 2021.

The findings elucidate a need to alter public health policies and recommendations surrounding COVID-19 vaccination to reflect the impact of available boosters against circulating variants of concern during the ongoing pandemic.

Led by Soham Sinha, MS, and Tamara Konetzka, PhD, each of the Biological Sciences Division, investigators sought to interpret the extent to which nursing home staff vaccination was linked to prevented COVID-19 cases and deaths among facility staff and residents over the span of 18 months. At the time of their research publication, US nursing home staff and residents accounted for more than 2 million COVID-19 cases and 155,000 deaths.

“Research has shown that higher staffing ratios were helpful in containing outbreaks in nursing homes,” they wrote. “However, studies have also found that more staff traffic between facilities and in and out of areas with high virus prevalence was associated with more cases and deaths in the nursing homes where the staff worked. To mitigate this risk, when vaccines became available in December 2020, staff and residents in nursing homes were among the first to be deemed eligible for vaccination.”

With the introduction of 2-dose mRNA COVID-19 vaccines to the general public under Emergency Use Authorization (EUA) in December 2020, utility of the initially efficacious regimen was mixed among nursing home residents and staff, respectively. Eventually, a federal mandate was established requiring health care workers be vaccinated in November 2021.

“The evidence base on the effectiveness of the mandate in preventing COVID-19 cases among nursing home residents is weak,” Sinha and Konetzka argued. “Thus, ongoing policy around staff vaccinations has been made in the absence of a robust evidence base.”

The team included data from residents of 15,000-plus US nursing homes that reported their COVID-19 incidence to the Centers for Disease Control and Prevention (CDC) and passed Centers for Medicare & Medicaid Services data quality checks through the National Healthcare Safety Network. Their primary outcomes were weekly COVID-19 cases and deaths among nursing home residents, and weekly COVID-19 cases among staff; treatment variable was the primary 2-dose staff vaccination among each facility’s staff weekly.

Their final analysis included 15,042 nursing homes observed prior to the Omicron variant wave, from May 30 – December 5, 2021. In that time period, increasing weekly staff vaccination rates by 10 percentage points was associated with 0.13 fewer weekly COVID-19 cases per 1000 residents (95% CI, -.20 to -.10), 0.02 fewer weekly COVID-19 deaths per 1000 residents (95% CI, -0.03 to -0.01) and 0.03 fewer weekly COVID-19 staff cases (95% CI, -0.04 to -0.02).

Extrapolated to a full year, the estimates would imply mean prevention of 10.29 COVID-19 cases per 1000 residents, 15.6 COVID-19 deaths per 1000, and approximately 21,000 total staff cases.

“The results show a dose-response pattern and an association with lower adverse COVID-19 outcomes at the highest rates of vaccination,” investigators wrote. “Our primary analysis found that highest rates of staff vaccinations were associated with protection to residents and staff amidst both a surging prevalence of virus in the community and a changing landscape of COVID-19–safe practices in nursing homes.”

However, in these facilities during the Omicron wave from December 5, 2021 – January 30, 2022, increasing staff vaccination rates were no longer associated with decreased rates of resident cases and deaths, nor staff cases.

“Newer strains of the COVID-19 virus such as Omicron and its subvariants have been found to be more transmissible than the previous strains of the virus,” investigators wrote. “This suggests that going forward, additional booster doses for staff may be needed to effectively manage the pandemic in nursing homes.”

The team concluded that COVID-19 vaccination has provided a relief in COVID-19 cases and deaths among nursing home residents and staffs, despite inconsistencies in initial uptake and fluctuation in efficacy based on circulating SARS-CoV-2 strains. With booster dose uptake now generally low among nursing home staffs, they recommended updated perspective around vaccination policies.

“Going forward, policy makers should take note of the existing evidence base on the association of staff vaccination rates with COVID-19 outcomes in nursing homes and use that to guide efforts to optimize policy,” they wrote. “Evolving evidence-based policy will be critical.”

The study, “Association of COVID-19 Vaccination Rates of Staff and COVID-19 Illness and Death Among Residents and Staff in US Nursing Homes,” was published online in JAMA Network Open.