U.K. vaccine chief says COVID-19 vaccine may be 50 percent effective. Her U.S. counterpart is more bullish.

The first wave of COVID-19 vaccines probably won't end the coronavirus pandemic, but "a partially effective vaccine is better than no vaccine at all," Kate Bingham, the head of Britain's vaccine task force, told Sky News on Tuesday. "Flu vaccines are 50 percent effective, but they are widely used and have a big impact on reducing the clinical impacts of flu in the population." She told The Telegraph on Wednesday that with the COVID-19 effort, "we shouldn't assume it's going to be better than a flu vaccine."

Bingham said British regulators are expecting data from two Phase 3 vaccine trials, from Oxford University-AstraZeneca and Pfizer-BioNTech, within weeks. "We haven't seen any serious safety signals that have stopped these vaccines completely," she said. "There will of course be safety issues, but these are carefully monitored."

In the U.S., the Food and Drug Administration won't approve any COVID-19 vaccine that is less that 50 percent effective at preventing infection or reducing severity, and Dr. Anthony Fauci, the nation's top infectious disease expert, said in August that "we don't know" if it will be any more effective than that. But Moncef Slaoui, chief scientific adviser to the U.S. government's Operation Warp Speed vaccine initiative, "has said repeatedly that he expects some of the candidates that he picked to have 75 to 90 percent efficacy and at least two to win approval by early January," Donald G. McNeil Jr. writes at The New York Times.

"Since January, when I began covering the pandemic, I have been a consistently gloomy Cassandra," McNeil writes. But "events have moved faster than I thought possible. I have become cautiously optimistic. Experts are saying, with genuine confidence, that the pandemic in the United States will be over far sooner than they expected, possibly by the middle of next year," and in the meantime, "the rest of us know what we need to do."

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