COVID-19 vaccines has come under controlled conditions in clinical trials, leaving an element of uncertainty over how results would translate into the real world with its unpredictable variables.The research in Israel - two months into one of the world's fastest rollouts, providing a rich source of data - showed two doses of the Pfizer shot cut symptomatic COVID-19 cases by 94% across all age groups, and severe illnesses by nearly as much.The study of about 1.2 million people also showed a single shot was 57% effective in protecting against symptomatic infections after two weeks, according to the data published and peer-reviewed in the New England Journal of Medicine on Wednesday.The results of the study for the Clalit Research Institute.