Pfizer, BioNTech initial vaccine results impress, but scientists remain cautious

Scientists on Monday said initial trial results for Pfizer Inc and BioNTech's coronavirus vaccine far outpaced their expectations for protection against a completely new disease, but that many questions remain unanswered.

The drugmakers said their vaccine was more than 90 percent effective at preventing Covid-19, based on data from the first 94 people in the trial to become infected with the coronavirus...