What we know — and don’t — about Pfizer’s promising vaccine results

The better-than-expected result is the first Phase III data from any of the four candidates now in the final stage of testing in the U.S. But there are still many questions about the vaccine and when it might be available for use.

Scientists are happy — but want more data

“I can’t imagine better news on the vaccine front,” said Walid Gellad, director for the Center for Pharmaceutical Policy and Prescribing at the University of Pittsburgh. “Not only is it highly effective based on the press release, but there were 90 cases so we don’t have to deal with the skeptics about interim analyses, and there appeared to be no safety signals.”

Others noted that the information Pfizer had released was promising but still incomplete, and had not been peer-reviewed or published in a scientific journal. “We should remain a little cautious, said Michael Head, a senior research fellow in global health at the University of Southampton in the U.K. “The provisional findings are made available in a press release, and the study is ongoing.”

One important question is how long immune protection from the vaccine will last. The limited data that Pfizer released only reveals how the vaccine performed seven days after the second of two doses.

It’s also not clear yet how well the vaccine will work for the elderly, whose immune systems are generally weaker than those of younger adults and children. A preliminary study suggested that older adults respond to the vaccine, but not as strongly as young or middle-aged people do.

Pfizer’s trial is also examining how well the vaccine works in people of color, who have been hospitalized and died at disproportionately high rates in the U.S., and in children as young as 12.

Paul Offit, a University of Pennsylvania vaccine expert who co-developed the rotavirus vaccine, said the early results were “very good news.” But he would like to see data on how the shot performs in various sub-groups, including the elderly, and whether anyone in the trial developed severe Covid-19.

Politicians cheered the news

President Donald Trump, who pushed unsuccessfully for a vaccine by Election Day, applauded the Pfizer result. “STOCK MARKET UP BIG, VACCINE COMING SOON. REPORT 90% EFFECTIVE. SUCH GREAT NEWS!” he wrote on Twitter.

President-Elect Joe Biden issued a statement congratulating “the brilliant women and men who helped produce this breakthrough,” but cautioned that “the end of the battle against COVID-19 is still months away.”

Even if a shot is authorized by late November, it will take many months before vaccination is widespread, Biden noted. “Americans will have to rely on masking, distancing, contact tracing, hand washing, and other measures to keep themselves safe well into next year,” he said.

Vice President Mike Pence was quick to give credit to the Trump Administration’s vaccine and drug accelerator, Operation Warp Speed, in a tweet this morning.

“HUGE NEWS,” he wrote. “Thanks to the public-private partnership forged by President @realDonaldTrump, @pfizer announced its Coronavirus Vaccine trial is EFFECTIVE, preventing infection in 90% of its volunteers.”

But company officials had already distanced themselves from the administration, with Pfizer’s head of vaccine research and development, Kathrin Jansen, telling the New York Times that “we were never part of the Warp Speed.”

She added: “We have never taken any money from the U.S. government, or from anyone.”

That’s not entirely true. The company did not accept money from the government to help support the development of its shot, as some other vaccine makers did. But Pfizer inked a contract with the government in July to deliver millions of doses.