Effectiveness of a COVID-19 Additional Primary or Booster Vaccine Dose in Preventing SARS-CoV-2 Infection Among Nursing Home Residents During Widespread Circulation of the Omicron Variant - United States, February 14-March 27, 2022

Abstract

Nursing home residents have experienced disproportionally high levels of COVID-19-associated morbidity and mortality and were prioritized for early COVID-19 vaccination (1). Following reported declines in vaccine-induced immunity after primary series vaccination, defined as receipt of 2 primary doses of an mRNA vaccine (BNT162b2 [Pfizer-BioNTech] or mRNA-1273 [Moderna]) or 1 primary dose of Ad26.COV2 (Johnson & Johnson [Janssen]) vaccine (2), CDC recommended that all persons aged ≥12 years receive a COVID-19 booster vaccine dose.* Moderately to severely immunocompromised persons, a group that includes many nursing home residents, are also recommended to receive an additional primary COVID-19 vaccine dose.^† Data on vaccine effectiveness (VE) of an additional primary or booster dose against infection with SARS-CoV-2 (the virus that causes COVID-19) among nursing home residents are limited, especially against the highly transmissible B.1.1.529 and BA.2 (Omicron) variants. Weekly COVID-19 surveillance and vaccination coverage data among nursing home residents, reported by skilled nursing facilities (SNFs) to CDC's National Healthcare Safety Network (NHSN)^§ during February 14-March 27, 2022, when the Omicron variant accounted for >99% of sequenced isolates, were analyzed to estimate relative VE against infection for any COVID-19 additional primary or booster dose compared with primary series vaccination. After adjusting for calendar week and variability across SNFs, relative VE of a COVID-19 additional primary or booster dose was 46.9% (95% CI = 44.8%-48.9%). These findings indicate that among nursing home residents, COVID-19 additional primary or booster doses provide greater protection against Omicron variant infection than does primary series vaccination alone. All immunocompromised nursing home residents should receive an additional primary dose, and all nursing home residents should receive a booster dose, when eligible, to protect against COVID-19. Efforts to keep nursing home residents up to date with vaccination should be implemented in conjunction with other COVID-19 prevention strategies, including testing and vaccination of nursing home staff members and visitors.

FIGURE

Crude weekly rates of reported confirmed SARS-CoV-2 infection among skilled nursing facility residents, by vaccination status and resident-week — National Healthcare Safety Network, United States, February 14–March 27, 2022 * Crude rates of SARS-CoV-2 infection were calculated as the number of cases, by vaccination status, among residents with corresponding vaccination status from 2 weeks earlier (January 31–March 13, 2022); 95% CIs indicated by error bars. ^† Residents who completed a primary vaccination series were those who received 2 primary doses of an mRNA vaccine (Pfizer-BioNTech or Moderna) or 1 primary dose of Janssen vaccine. Residents with additional or booster dose vaccination were those who received an additional primary vaccine dose ≥28 days after the initial primary series or a booster dose ≥5 months after completion of an mRNA primary series or ≥2 months after 1 primary Janssen vaccine dose. Residents with an additional or booster dose included those who received additional primary vaccine doses and a booster dose. Unvaccinated residents were those who received no COVID-19 vaccine doses. Cases among residents with primary series vaccination were defined as infections in residents who had received primary series vaccination ≥14 days before a SARS-CoV-2–positive test result or received an additional or booster dose <14 days before a SARS-CoV-2–positive test result. Cases among residents with additional or booster dose vaccination were defined as infections in residents who received an additional primary or booster dose ≥14 days before a SARS-CoV-2–positive test result. Cases among unvaccinated residents were defined as infections in residents who received no COVID-19 vaccine doses or a single dose <14 days before a SARS-CoV-2–positive test result. Data on infections among residents who received a single dose of mRNA vaccine ≥14 days before a SARS-CoV-2–positive test result or unspecified vaccination are not presented. ^§ Resident-weeks were calculated as the aggregate of weekly resident counts, by vaccination status, at each skilled nursing facility.