Preprints with The Lancet is part of SSRN´s First Look, a place where journals identify content of interest prior to publication. Authors have opted in at submission to The Lancet family of journals to post their preprints on Preprints with The Lancet. The usual SSRN checks and a Lancet-specific check for appropriateness and transparency have been applied. Preprints available here are not Lancet publications or necessarily under review with a Lancet journal. These preprints are early stage research papers that have not been peer-reviewed. The findings should not be used for clinical or public health decision making and should not be presented to a lay audience without highlighting that they are preliminary and have not been peer-reviewed. For more information on this collaboration, see the comments published in The Lancet about the trial period, and our decision to make this a permanent offering, or visit The Lancet´s FAQ page, and for any feedback please contact email@example.com.
BNT162b2 Vaccine Effectiveness in Preventing Asymptomatic Infection with SARS-CoV-2 Virus: A Nationwide Historical Cohort Study
14 Pages Posted: 3 Mar 2021More...
Background: There is strong evidence regarding the efficacy and effectiveness of BNT162b2 vaccine in preventing symptomatic infection with SARS-CoV-2 virus. There is a paucity of data regarding effectiveness in prevention of asymptomatic infection.
Methods: In this real-world study, we identified a sub-population of patients in a large health maintenance organisation who were repeatedly tested for SARS-CoV-2 infection using a PCR test. We used these patients as the cohort for the study, and compared individuals who were vaccinated with BNT162b2 mRNA vaccine to the unvaccinated ones. A positive SARS-CoV-2 PCR test result was used as the outcome. Follow-up period was from Jan 1,2021 until Feb 11, 2021.
Findings: 6,286 individuals were included in the cohort. Seven days following the second vaccine dose, a rate of six positive PCR tests per 10,000 patient-days was recorded, compared with a rate of 53 positive tests per 10,000 patient-days for the unvaccinated group. The estimated vaccine effectiveness against infection with SARS-CoV-2 virus after two vaccine doses was 89% (confidence interval 82%-94%). The estimated effectiveness two weeks following the first vaccine dose was 61% (confidence interval 49%-71%).
Interpretation: In this study, vaccination with BNT162b2 reduced infection rates among individuals who underwent screening by frequent SARS-CoV-2 PCR testing. Using a cohort of frequently tested individuals reduced the indication bias for the PCR testing, which enabled estimation of asymptomatic infection rates.
Funding: This study received no funding.
Declaration of Interests: DS reports receiving personal fees from Pfizer, outside the submitted work (advisory board on Trumenba); and Consultation fees from GSK and Gilead. The other authors declare no competing interests.
Ethics Approval Statement: This study was approved by MHMO’s institutional review board number 03-17-02- 21, and investigators were exempt from requesting informed consent.
Suggested Citation: Suggested Citation