Pfizer Inc. reported on November 9th that its Covid-19 vaccine may be 90% effective. Dr. Anthony Fauci, the U.S.'s top infectious disease expert, said that level of effectiveness is “just extraordinary,” adding: “Not very many people expected it would be as high as that.” The hopeful news comes as the U.S. crosses 10 million Covid cases, the highest in the world. While optimistic, the announcement, from an independent data monitoring board, is tempered with unknowns as well: it "looked at 94 infections recorded so far in a study that has enrolled nearly 44,000 people in the U.S. and five other countries," the Associated Press reports. Pfizer released no specific breakdowns, but for the vaccine to be 90% effective, nearly all placebo recipients must have had infections, and the pharmaceutical company cautioned that the protection rate might change as more cases are added to calculations. While many questions still remain, experts such as Dr. Jesse Goodman at Georgetown University (and former chief of the FDA’s vaccine division) call the partial results "extremely promising."