Study population and setting
This study looked at effectiveness of the Pfizer-BioNTech BNT162b2 mRNA vaccine in Qatar’s national vaccination campaign. Data from standardized national SARS-CoV-2 databases compiled at Hamad Medical Corporation, the principal public healthcare provider and designated provider for COVID-19 healthcare needs in Qatar, was used for the analysis. Vaccinations began on December 21, 2020, and by March 31, 2021 over 300,000 individuals had at least one dose of vaccine and over 250,000 individuals had two doses. The authors extracted data from February 1 to March 31, 2021, which coincided with the rapid scale-up of vaccinations in Qatar during its second and third waves of SARS-CoV-2 infection. Data included PCR testing results, antibody testing results, COVID-19 hospitalizations, vaccinations, infection severity, and COVID-19 deaths. Estimated vaccine effectiveness was calculated using a test-negative, case-control study design. Inclusion criteria were a B.1.1.7 case (UK variant), a B.1.351 case (South African variant), or a severe, critical, or fatal disease case. Cases and controls were matched one-to-one by age, sex, nationality, and reason for PCR testing.
Summary of Main Findings
The BNT162b2 vaccine’s effectiveness against the B.1.1.7 (UK) variant was estimated to be 89.5%, and 75% against the B.1.351 (South African) variant. Effectiveness against severe, critical, or fatal disease due to infection with any SARS-CoV-2 variant was estimated to be 97.4%, with B.1.1.7 and B.1.351 being most predominant variants in circulation. When comparing incidence of infection between vaccinated individuals and those who were antibody negative, it was estimated that there was an 87% effectiveness against the B.1.1.7 variant and 72.1% effectiveness against the B.1.351, confirming results from the previous analysis. Effectiveness against the B.1.351 variant specifically was approximately 20% lower than the >90% effectiveness seen in clinical trials and real-world conditions in Israel and the US, but this did not affect the overall effectiveness seen in Qatar, which was well over 90%.
This retrospective analysis included a large sample size of over 200,000 individuals. Next, the test-negative, case-control study design is a widely accepted design used for assessing vaccine effectiveness against influenza. A key strength of this method is the ability to control for bias from different healthcare-seeking behaviors of vaccinated and unvaccinated people. Finally, Qatar has unusual demographics by sex and nationality, with 89% of the population comprised of expatriates from over 150 countries. The wide range in nationalities could have added strength to the real-world value of this analysis due to an increased variety of ethnicities.
Due to the unique demographic of Qatar’s population, the median age included in the analysis was very low, with the median age in each group ranging from 32 to 43 years old and most included individuals under 40 years old. There was also a much greater proportion of males included in the analysis compared to females. Lastly, the effectiveness of the BNT162b2 vaccine against the B.1.351 variant was only assessed from March 8 – 31, during its wave of rapid expansion.
This is one of the first real-world vaccine effectiveness studies published about the Pfizer-BioNTech BNT162b2 mRNA vaccine, which documented Qatar’s national immunization campaign, and is yet another demonstrating that the vaccine is highly effective.
This review was posted on: 14 May 2021