Up-to-Date COVID-19 Vaccination and Infection in Nursing Home Residents, November 2022 to January 2023

This page describes a study and the vaccination guidance in force when it was published. COVID-19 vaccine recommendations have changed since; check current CDC guidance.

Nursing home residents have been hit especially hard by COVID-19. Their age, other illnesses and shared living quarters put them at high risk of infection and of severe outcomes, including death. The primary mRNA vaccine series and monovalent boosters were already known to reduce illness and death in this group. What was not known was how well being "up to date" — which, from October 2022, largely meant having had a bivalent dose — protected residents against infection.

A CDC team used the National Healthcare Safety Network (NHSN) to find out, looking at November 20, 2022, through January 8, 2023.

What "up to date" meant

During the study, NHSN counted a resident as up to date if they had ever received a bivalent mRNA dose, or had completed a primary series less than 2 months earlier. Everyone else was "not up to date," a group mixing residents who had monovalent boosters but no bivalent dose, residents whose primary series was older with nothing since, residents with only 1 dose of a primary series, and residents never vaccinated.

Where the data came from

The Centers for Medicare & Medicaid Services requires certified nursing homes to report new COVID-19 cases and vaccination figures to NHSN every week. The analysis used homes that reported both, every week of the study, and dropped homes whose figures failed data-quality checks (for example, more residents than occupied beds, or signs of weekly rather than cumulative reporting).

Researchers compared infection rates in the two groups using a statistical model that accounted for calendar week, the county's COVID-19 incidence, the county's social vulnerability index, and the share of the home's staff who were up to date. An infection counted in the up-to-date group only if the resident had become up to date at least 14 days before testing positive.

Results

The analysis covered 108,727 weekly reports from 14,464 nursing homes.

• Every week, incidence was lower among up-to-date residents (7.6–15.3 cases per 1,000 residents) than among the others (11.1–19.1).
• The adjusted rate ratio was 0.69, giving a vaccine effectiveness against infection of 31.2% (95% confidence interval 29.1%–33.2%).
• The weekly share of residents who were up to date rose from 44.2% to 51.2%.

How to read it

A separate NHSN analysis found that more than 99% of up-to-date residents had received a bivalent dose, so up to date effectively meant bivalent. And 88% of residents had had at least one primary-series dose, so most of the comparison group was at least partly vaccinated. The 31.2% is therefore the added benefit of the bivalent dose in a mostly vaccinated population, not protection compared with no vaccine.

The authors said the figure resembled other estimates of bivalent protection against infection in older adults, especially given that the study came 2.5–4 months after a bivalent dose was first recommended for this group. Estimates presented to CDC's Advisory Committee on Immunization Practices showed that protection against symptomatic infection among adults aged 65 and older waned over the months after a bivalent dose. The goal of the vaccination program is to prevent severe illness and death, and protection against those outcomes has been shown to be higher and longer-lasting than protection against infection.

Limitations

• The data covered infection only, not hospitalization or death.
• Facilities report totals, not individual records, so the study could not account for time since vaccination, earlier infection, symptoms or personal characteristics.
• With no group that had neither vaccine nor prior infection, effectiveness against no vaccination could not be calculated.
• Nursing homes' reports could not be checked against patient records, so some residents may have been misclassified.

What the authors recommended

Nursing home residents should stay up to date with age-appropriate COVID-19 vaccination, which at the time of the report included an additional bivalent dose for moderately or severely immunocompromised adults aged 65 and older.

Sources

• Wong E, Barbre K, Wiegand RE, et al. "Effectiveness of Up-to-Date COVID-19 Vaccination in Preventing SARS-CoV-2 Infection Among Nursing Home Residents — United States, November 20, 2022–January 8, 2023." Morbidity and Mortality Weekly Report 72(25), Centers for Disease Control and Prevention.
• The report gives two different dates for the February 2023 Advisory Committee presentation it cites (one in the text, another in its reference list); this page names neither.