The Pfizer vaccine appears to stop the spread of the coronavirus in the majority of recipients, according to an Israeli study.
The vaccine was 89.4% effective at preventing infection, according to a recent study that has not yet been peer reviewed. Israeli authorities said on Saturday that the vaccine was 99% effective at preventing deaths caused by COVID-19.
The study compared reported infections among those who had been vaccinated versus those who had not been vaccinated. Nearly half of the Israeli population has had at least one dose of the vaccine.
Some scientists pushed back on the study's results. Zoe McLaren, an associate professor in the school of public policy at the University of Maryland Baltimore County, said that study was not designed to accurately measure transmission because it did not account for varying testing rates between vaccinated and unvaccinated people. The study relied on national testing data.
"The main result overstates the reduction in transmission from the Pfizer vaccine," McLaren said. "...That means that the true reduction in transmission is lower than the estimate of 89.4%. How much lower? We need more evidence to know for sure. But I expect that, once we account for the bias, we'll still find that this vaccine does reduce transmission. And that would be very good news."