1. This observational cohort study demonstrated that among long-term care residents in Israel, the BNT162b2 (Pfizer-BioNTech) booster dose (third overall dose) was associated with reduced SARS-CoV-2 infections, hospitalizations, severe illness, and COVID-19-related death compared to two-dose-only vaccinees.
2. These findings suggest that vaccination with the booster dose (third overall dose) of BNT162b2 was key in controlling the spread of the Delta variant in the population of long-term care facilities.
Evidence Rating Level: 2 (Good)
Study Rundown: COVID-19 booster vaccination has emerged as an ongoing debate. Older adults vaccinated with two doses in January 2021 demonstrated a 1.6-fold increased risk of infection compared to those vaccinated in March 2021, which may suggest waning immunity. Individuals in long-term care facilities (LTCFs) are at high risk of severe or fatal COVID-19 and were one of the first cohorts to receive the first booster dose (third overall dose). This observational cohort study investigated whether receiving the BNT162b2 (Pfizer-BioNTech) third dose was associated with decreased infections, hospitalizations, and mortality compared to receiving only two doses. This study was conducted in Israel between August and October 2021 among LTCF residents ages 60 and over as part of the SARS-CoV-2 infection surveillance in LTCFs. The primary outcome was SARS-CoV-2 infection. Secondary outcomes included hospitalization, illness severity, and COVID-19-related death. Follow-up was greater than seven days after vaccination with the third dose. Sixteen thousand eighty-two individuals received the third dose compared to 2529 residents who received only two doses at least five months before the follow-up start date. Third-dose vaccination was associated with a reduced risk of SARS-CoV-2 infection compared to two-dose-only vaccinees (adjusted hazard ratio [aHR]: 0.11 [95% CI: 0.07-0.14]). Furthermore, the cohort who received three doses had significantly reduced risk of hospitalization due to COVID-19 (aHR: 0.07 [95% CI: 0.03-0.15]), severe illness (aHR: 0.10 [95% CI: 0.04-0.24]), and COVID-19-related mortality (aHR: 0.04 [95% CI: 0.009-0.16]). Overall, this study demonstrated that receiving the BNT162b2 (Pfizer-BioNTech) booster dose was significantly associated with reduced SARS-CoV-2 infection, hospitalizations, severe illness, and death compared to those who received only two doses. One strength of this study is that data were extracted from the Senior Shield COVID-19 routine surveillance, where polymerase chain reaction (PCR) testing was done systematically and not based on vaccination status. However, this study was limited by the inherent nature of an observational cohort study design, as the decision to vaccinate may have been affected by selection bias.
Relevant Reading: Waning immunity after the BNT162b2 vaccine in Israel
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