- The extensive nationwide rollout of Israel’s third-dose ‘booster’ COVID-19 vaccination campaign provided the Clalit Research Institute with a unique opportunity
- This study suggests that a third vaccine dose is effective in reducing severe COVID-19-related outcomes
- The research was funded in part by the newly announced Ivan and Francesca Berkowitz Family Living Laboratory
The Clalit Research Institute,and researchers from Harvard University, analyzed one of the world’s largest health record databases to examine the effectiveness of the third dose of the Pfizer/BioNTech BNT162B2, reports Medical Lifesciences News.
About the study
The study provides the largest peer-reviewed evaluation of the effectiveness of a third “booster” dose of a COVID-19 vaccine in a nationwide mass-vaccination setting. The study was conducted in Israel, an early global leader in third-dose COVID-19 vaccination rates.
It is the first to estimate the effectiveness of a third dose of an mRNA COVID-19 vaccine-;BNT162b2 specifically-;against severe outcomes with adjustment for various possible confounders, including comorbidities and behavioral factors.
The study’s large size also allows a more precise assessment of the vaccine’s effectiveness across different time periods, different subpopulations, and different severe outcomes.
The study took place from July 30, 2021 through Sept 23, 2021, coinciding with Israel’s fourth wave of coronavirus infection and illness, during which the Delta (B.1.617.2) variant was the dominant strain in the country for new infections (with very few exceptions).
Source of data
Researchers reviewed data from 728,321 individuals aged 12 or above who had received the third dose of the BNT162b2 vaccine. These individuals were carefully matched 1:1 with 728,321 individuals who had received only two shots of the BNT162b2 vaccine at least five months prior.
The matching was based on an extensive set of demographic, geographic and health-related attributes associated with risk of infection, risk of severe disease, health status and health seeking behavior. Individuals were assigned to each group dynamically based on their changing vaccination status.
Multiple analyses were conducted to ensure that the estimated vaccine effectiveness was robust to potential biases. The study included a total of over 12,000,000 person-days of follow-up.
Outcome
This study suggests that a third vaccine dose is effective in reducing severe COVID-19-related outcomes compared to individuals who have received two vaccine doses at least 5 months ago.
The results show that, compared with individuals who received only two doses five months prior, individuals who received three doses of the vaccine had:
- 93% lower risk of COVID-19-related hospitalization,
- 92% lower risk of severe COVID-19 disease
- 81% lower risk of COVID-19-related death.
The study also included a population-level analysis which found that infection rates began to drop for each age group 7-10 days after that age group became eligible for the third dose.
Researcher’s opinion
“These results show convincingly that the third dose of the vaccine is highly effective against severe COVID-19-related outcomes in different age groups and population subgroups, one week after the third dose. These data should facilitate informed policy decision-making,” added Prof. Balicer, who also serves as Chairman of Israel’s National Expert Advisory Team on COVID-19 response.
Prof. Ben Reis, Director of the Predictive Medicine Group at the Boston Children’s Hospital Computational Health Informatics Program and Harvard Medical School, said, “To date, one of the main drivers of vaccine hesitancy has been a lack of information regarding the effectiveness of the vaccine. This careful epidemiological study provides reliable information on third-dose vaccine effectiveness, which we hope will be helpful to those who have not yet decided about vaccination with a third dose.”
Prof. Miguel Hernán, Director of the CAUSALab and Professor at the Harvard T.H. Chan School of Public Health, said, “This research is a perfect example of how randomized trials and observational healthcare databases complement each other. This combination of evidence from randomized trials and observational studies is a model for efficient medical research, something which is especially important in COVID times.”
“The strengthening of the scientific collaboration between Harvard and Clalit made possible by the Berkowitz Living Laboratory Collaboration is already bearing fruit and giving us a foretaste of the value of healthcare systems instrumented for research,” said Prof. Isaac Kohane, Chair of the Department of Biomedical Informatics at Harvard Medical School and co-Director of the Ivan and Francesca Berkowitz Family Living Laboratory Collaboration along with Professor Balicer.
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Source: Medical Lifesciences News
