Key Points

Question  What is the association of receiving the fourth dose of BNT162b2 vaccine with Omicron variant infection among residents of long-term care facilities?

Findings  In this cohort study of 24 088 recipients of a fourth dose of vaccine and 19 687 individuals who received a third dose only (4 months previously or earlier), receipt of the vaccine dose was associated with 34% protection against infection, 64% to 67% against hospitalizations for mild-to-moderate and severe illness, and 72% against deaths.

Meaning  The study results suggest that a fourth BNT162b2 dose was associated with high protection against COVID-19 hospitalizations and deaths among residents of long-term care facilities during a surge associated with the Omicron variant.

Importance  The administration of a fourth BNT162b2 COVID-19 vaccine dose was approved in Israel in December 2021 for individuals 60 years or older who were vaccinated with a third dose 4 months previously or earlier to control the substantial surge of the SARS-CoV-2 Omicron variant. Nonetheless, the association between receipt of the fourth dose and protection against infection remains elusive.

Objective  To determine the association of the fourth BNT162b2 dose with protection against SARS-CoV-2–related infections, hospitalizations, and deaths during the Omicron surge in long-term care facility (LTCF) residents.

Design, Setting, and Participants  This prospective cohort study was conducted in Israel between January 10 and March 31, 2022 and included LTCF residents 60 years or older.