MICHAEL ERMAN and JULIE STEENHUYSEN PFIZER Inc's experimental COVID-19 vaccine is more than 90% effective based on initial trial results, the drugmaker said, a major victory in the war against a virus that has killed over a million people and battered the world's economy. Experts welcomed the first successful interim data from a large-scale clinical test as a watershed moment that showed vaccines could help halt the pandemic, although mass roll-outs, which needs regulatory approval, will not happen this year. Pfizer and German partner BioNTech SE said they had found no serious safety concerns yet and expected to seek U.S.…