Results from an analysis of COVID-19 vaccination data from Israel, where most of the population have now been vaccinated, confirm earlier Phase III data and show over 90% protection from asymptomatic and symptomatic disease with the BioNTech/Pfizer vaccine.
Notably, this efficacy held true despite several variants of concern circulating in Israel at the time of vaccination, with the UK B.1.1.7 variant being the most common. While efficacy was good, there was a decrease in efficacy in much older individuals and those with serious chronic conditions like diabetes.
“Despite the benefits of a controlled trial, it is limited in resolution due to restrictions during the recruitment process and the relatively small sample size. For example, the phase III trial did not allow the participation of immunosuppressed patients, or patients with unstable chronic conditions,” write Roy Kishony, Ph.D., a professor at Technion – Israel Institute of Technology in Haifa, and colleagues in a paper published as a preprint on the medRxiv server, which has not yet been peer reviewed.
“The rapid national vaccination rollout in Israel provides an opportunity to test the effectiveness of the vaccine in real-world prevention of SARS-CoV-2 infection and disease across a diverse population. However, estimating the real-world effectiveness of the vaccine is challenging due to strong temporal and spatial epidemic patterns, and association of testing with vaccination.”
Israel stands out over other countries around the world for the speed with which it rolled out a national vaccine campaign against SARS-CoV-2 as soon as feasibly possible. According to recent figures, the country has already completely vaccinated 48.2% (4.5 million people) of its citizens using the BioNTech/Pfizer vaccine.
This study included the 1.2 million Israeli citizens vaccinated with the BioNTech/Pfizer vaccine by Maccabi Healthcare Services, one of the main health insurers in the country, between December 2020 and February 2021.
The researchers found that the efficacy of the vaccine gradually increased after 12 days, reaching a plateau at day 35. The overall effectiveness of the vaccine in this cohort was 91.2% against all infections and 99.3% against symptomatic infections.
The team found that the efficacy of the vaccine was similar in people aged 16—80 and also in men and women, but started to decrease slowly but significantly in older groups. It was also less effective at protecting high-risk individuals with significant medical conditions, particularly those with immunosuppression, COPD or diabetes.
Although every attempt was made to minimize error and correct for possible confounding factros, Kishony and team acknowledge that their study was observational and could therefore be subject to bias. For example, there could be overall health differences between the vaccinated and unvaccinated groups.
However, they conclude: “Our methodology provides a unified framework for analyzing vaccine effectiveness and its dependence on patient’s attributes from dynamic spatially distributed datasets… Quantifying real-world vaccine effectiveness, including both biological and behavioral effects, our analysis provides initial measurement of vaccine effectiveness across demographic groups.”