The U.S. has ordered 100 million doses of a potential COVID-19 vaccine from drug giant Pfizer as part of Operation Warp Speed, the White House effort to expedite a national coronavirus inoculation. If the vaccine proves safe and effective in humans, the government has agreed to pay $1.95 billion for Pfizer to produce and deliver the shots, which are being developed with German biotech firm BioNTech, the Department of Health and Human Services said Wednesday. The vaccine would be made available to Americans at no cost, the HHS said. Under the agreement, the U.S. could acquire an additional 500 million doses. Shares of Pfizer rose more than 4 percent in pre-market trading on the news. HHS Secretary Alex Azar says the department was developing a “portfolio of vaccines to increase the odds that the American people will have at least one safe, effective vaccine as soon as the end of this year.”