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

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 * During September-October, 2021, CDC recommended use of a single COVID-19 vaccine booster dose for all persons aged 18 years, 6 months after receipt of a primary mRNA vaccination series or 2 months after receipt of a primary Janssen vaccine dose. During January, 2022, CDC updated booster recommendations, shortening the interval from 6 months to 5 months for receiving an mRNA booster dose after a primary mRNA vaccination series. In January, 2022, CDC also expanded eligibility of booster doses, recommending that adolescents aged 12-17 years receive a booster dose 5 months after a primary Pfizer-BioNTech vaccination series. https://www.cdc.gov/vaccines/covid-19/ clinical-considerations/covid- 19-vaccines-us.html (Accessed March 27, 2022). https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/ immuno.html (Accessed March 27, 2022). CDC's NHSN provides health care facilities, such as skilled nursing and longterm care facilities with a platform for reporting outcomes and process measures. COVID-19 related vaccination and surveillance data are reported to NHSN through the long-term care facilities COVID-19 Module. https://www.cdc. gov/nhsn/ltc/covid19/index.html