An experimental COVID-19 vaccine from Pfizer Inc and BioNTech SA appears to be more than 90% effective, based on data analyzed midway through a gold-standard clinical trial, the companies announced on Monday. Pfizer said researchers had analyzed 94 confirmed cases of COVID-19 in trial participants and found the vast majority of the infections were in volunteers in the placebo group. BioNTech's co-founder and chief executive said he was optimistic that the protective effect of the experimental COVID-19 vaccine would last for at least a year.