Researchers at Israel’s Sheba Medical Center have published the results of their study on medical staff, showing the Pfizer Covid-19 vaccine to be 75% effective two to four weeks after a single shot. Many countries were pleased to know that they were right to prioritize the first shot.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00448-7/fulltext