The short version is that initial data out of Israel appears to show dramatically increased protection both against infection and disease from a third dose. But there are at least some questions about the data and what they actually mean.
There are two studies or at least two sources of data. One is from Maccabi Health Services, one of the four HMOs that makes up the Israeli national health care system. They looked at 149,144 people who had gotten a third booster and 675,630 who had two shots. Only 37 people in the first group had gotten infected compared to 1,064 of the latter. The booster shot cut the risk of infection by 86% and the risk of severe disease by 92%.
