Effectiveness of a third dose of the BNT162b2 mRNA COVID-19 vaccine for preventing severe outcomes in Israel: an observational study

Noam Barda; Noa Dagan; Cyrille Cohen; Miguel A Hernán; Marc Lipsitch; Isaac S Kohane; Ben Y Reis; Ran D Balicer

doi:10.1016/S0140-6736(21)02249-2

Effectiveness of a third dose of the BNT162b2 mRNA COVID-19 vaccine for preventing severe outcomes in Israel: an observational study

Lancet. 2021 Dec 4;398(10316):2093-2100. doi: 10.1016/S0140-6736(21)02249-2. Epub 2021 Oct 29.

Authors

Noam Barda¹, Noa Dagan¹, Cyrille Cohen², Miguel A Hernán³, Marc Lipsitch⁴, Isaac S Kohane⁵, Ben Y Reis⁶, Ran D Balicer⁷

Affiliations

¹ Clalit Research Institute, Innovation Division, Clalit Health Services, Tel Aviv, Israel; Software and Information Systems Engineering, Ben Gurion University of the Negev, Be'er Sheva, Israel; Department of Biomedical Informatics, Harvard Medical School, Boston, MA, USA; The Ivan and Francesca Berkowitz Family Living Laboratory Collaboration at Harvard Medical School and Clalit Research Institute, Boston, MA, USA.
² The Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel.
³ Department of Epidemiology, Harvard T H Chan School of Public Health, Boston, MA, USA; Department of Biostatistics, Harvard T H Chan School of Public Health, Boston, MA, USA; CAUSALab, Harvard T H Chan School of Public Health, Boston, MA, USA.
⁴ Department of Epidemiology, Harvard T H Chan School of Public Health, Boston, MA, USA; Department of Immunology and Infectious Diseases, Harvard T H Chan School of Public Health, Boston, MA, USA; Center for Communicable Disease Dynamics, Harvard T H Chan School of Public Health, Boston, MA, USA.
⁵ Department of Biomedical Informatics, Harvard Medical School, Boston, MA, USA; The Ivan and Francesca Berkowitz Family Living Laboratory Collaboration at Harvard Medical School and Clalit Research Institute, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
⁶ The Ivan and Francesca Berkowitz Family Living Laboratory Collaboration at Harvard Medical School and Clalit Research Institute, Boston, MA, USA; Predictive Medicine Group, Computational Health Informatics Program, Boston Children's Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
⁷ Clalit Research Institute, Innovation Division, Clalit Health Services, Tel Aviv, Israel; School of Public Health, Faculty of Health Sciences, Ben Gurion University of the Negev, Be'er Sheva, Israel; The Ivan and Francesca Berkowitz Family Living Laboratory Collaboration at Harvard Medical School and Clalit Research Institute, Boston, MA, USA. Electronic address: [email protected].

Abstract

Background: Many countries are experiencing a resurgence of COVID-19, driven predominantly by the delta (B.1.617.2) variant of SARS-CoV-2. In response, these countries are considering the administration of a third dose of mRNA COVID-19 vaccine as a booster dose to address potential waning immunity over time and reduced effectiveness against the delta variant. We aimed to use the data repositories of Israel's largest health-care organisation to evaluate the effectiveness of a third dose of the BNT162b2 mRNA vaccine for preventing severe COVID-19 outcomes.

Methods: Using data from Clalit Health Services, which provides mandatory health-care coverage for over half of the Israeli population, individuals receiving a third vaccine dose between July 30, 2020, and Sept 23, 2021, were matched (1:1) to demographically and clinically similar controls who did not receive a third dose. Eligible participants had received the second vaccine dose at least 5 months before the recruitment date, had no previous documented SARS-CoV-2 infection, and had no contact with the health-care system in the 3 days before recruitment. Individuals who are health-care workers, live in long-term care facilities, or are medically confined to their homes were excluded. Primary outcomes were COVID-19-related admission to hospital, severe disease, and COVID-19-related death. The third dose effectiveness for each outcome was estimated as 1 - risk ratio using the Kaplan-Meier estimator.

Findings: 1 158 269 individuals were eligible to be included in the third dose group. Following matching, the third dose and control groups each included 728 321 individuals. Participants had a median age of 52 years (IQR 37-68) and 51% were female. The median follow-up time was 13 days (IQR 6-21) in both groups. Vaccine effectiveness evaluated at least 7 days after receipt of the third dose, compared with receiving only two doses at least 5 months ago, was estimated to be 93% (231 events for two doses vs 29 events for three doses; 95% CI 88-97) for admission to hospital, 92% (157 vs 17 events; 82-97) for severe disease, and 81% (44 vs seven events; 59-97) for COVID-19-related death.

Interpretation: Our findings suggest that a third dose of the BNT162b2 mRNA vaccine is effective in protecting individuals against severe COVID-19-related outcomes, compared with receiving only two doses at least 5 months ago.

Funding: The Ivan and Francesca Berkowitz Family Living Laboratory Collaboration at Harvard Medical School and Clalit Research Institute.

Publication types

Observational Study

MeSH terms

Adult
Aged
BNT162 Vaccine*
COVID-19 / epidemiology
COVID-19 / prevention & control*
COVID-19 / virology
Female
Humans
Immunization, Secondary*
Israel / epidemiology
Male
Mass Vaccination
Middle Aged
Pandemics / prevention & control
Prognosis
SARS-CoV-2
Vaccine Efficacy*

Substances

BNT162 Vaccine

Supplementary concepts

SARS-CoV-2 variants