Early humoral and cellular responses after bivalent SARS-CoV-2 mRNA-1273.214 vaccination in long-term care and retirement home residents in Ontario, Canada: An observational cohort study.

Immunogenicity of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) bivalent mRNA-1273.214 vaccine (Original/Omicron B.1.

Early Omicron infection is associated with increased reinfection risk in older adults in long-term care and retirement facilities.

Background: Older adults are at increased risk of SARS-CoV-2 Omicron infection and severe disease, especially those in congregate living settings, despite high SARS-CoV-2 vaccine coverage. It is unclear whether hybrid immunity (combined vaccination and infection) after one Omicron infection provides increased protection against subsequent Omicron reinfection in older adults.

Methods: Incidence of SARS-CoV-2 Omicron infection was examined in 750 vaccinated residents of long-term care and retirement homes in the observational cohort in Ontario, Canada, within a 75-day period (July to September 2022).

Protection from Omicron Infection in Residents of Nursing and Retirement Homes in Ontario, Canada.

Objectives: To identify factors that contribute to protection from infection with the Omicron variant of SARS-CoV-2 in older adults in nursing and retirement homes.

Design: Longitudinal cohort study with retrospective analysis of infection risk.

Setting And Participants: 997 residents of nursing and retirement homes from Ontario, Canada, in the COVID in LTC study.