As the Delta variant sweeps the world, researchers are tracking how well vaccines protect against it — and getting different answers. In Britain, researchers reported in May that two doses of the Pfizer-BioNTech vaccine had an effectiveness of 88 percent protecting against symptomatic disease from Delta. A June study from Scotland concluded that the vaccine was 79 percent effective against the variant. On Saturday, a team of researchers in Canada pegged its effectiveness at 87 percent. And on Monday, Israel’s Ministry of Health announced that the effectiveness of the Pfizer-BioNTech vaccine was 64 percent against all coronavirus infections, down from about 95 percent in May, before the Delta variant began its climb to near-total dominance in Israel. Although the range of these numbers may seem confusing, vaccine […]