Tel Aviv University and Clalit Health Services. They compared more than 400 people who received at least one shot of Pfizer’s two-dose vaccine and contracted the virus to 400 people who had not been vaccinated and became infected.People infected at least a week after the second dose were infected with the South African variant (B.1.351) at a ratio of 8:1, the study found.In this photo illustration, various medical syringes seen with the Pfizer company logo displayed on a screen in the background.