AstraZeneca insisted late Wednesday that its COVID-19 vaccine is strongly effective even after including additional illnesses in its disputed U.S. study, the latest in an extraordinary public rift with American officials.
In a late-night press release, the British drug maker said it had recalculated data from that advanced trial and concluded the vaccine is 76% effective in preventing symptomatic COVID-19, instead of the 79% it had claimed earlier in the week.
Just a day earlier, an independent panel that oversees the study had accused AstraZeneca of cherry-picking data to tout the protection offered by its vaccine. The panel, in a harsh letter to the company and to U.S. health leaders, said the company had left out some COVID-19 cases that occurred in the study, a move that could erode trust in the science.
Data disputes during ongoing studies usually remain confidential but in an unusual step, the National Institutes of Health publicly called on AstraZeneca to fix the discrepancy.
AstraZeneca had been counting on findings from a predominantly U.S. study of 32,000 people to help rebuild confidence in a vaccine that, despite being widely used in Britain, Europe and other countries, has had a troubled rollout. Previous studies have turned up inconsistent data about its effectiveness, and then last week a scare about blood clots had some countries temporarily pausing inoculations.
Now the question is whether the company's newest calculations end the tension.
Earlier Wednesday, Dr. Anthony Fauci, the top U.S. infectious disease expert, told reporters he hoped that when all the data was publicly vetted by federal regulators, it would dispel any hesitancy caused by the spat. He predicted it would "turn out to be a good vaccine."
Paul Griffin, a professor at the University of Queensland in Australia, told the Reuters news service, "This appears to be a very effective vaccine with no safety concerns. Hopefully, this should now give people the confidence that this vaccine is the right one to continue to use moving forward."
William Schaffner, professor of infectious diseases at the Vanderbilt University School of Medicine, noted to Reuters, "The vaccine efficacy against severe disease, including death, puts the AstraZeneca vaccine in the same ballpark as the other vaccines."
AstraZeneca's newest calculations were based on 190 COVID-19 cases that occurred during the study, 49 more than it had included earlier in the week. The vaccine appears especially protective against the worst outcomes, with no severe illnesses or hospitalizations among vaccinated study volunteers compared to eight severe cases among those given placebo shots, the company said. It didn't provide a breakdown of the rest of the cases.
European authorities had questioned how protective the vaccine is in older adults. In the U.S. study, it was 85% effective in volunteers 65 and older, the company said. The study didn't turn up safety concerns.
The updated information "confirms that our COVID-19 vaccine is highly effective in adults, including those aged 65 years and over," AstraZeneca research chief Mene Pangalos said in a statement. He said the company looks forward to "the rollout of millions of doses across America."
The study hasn't ended, so additional COVID-19 cases can accrue. AstraZeneca cautioned that 14 additional possible cases already are being examined, which could lead to further changes in the data.
The company intends to seek Food and Drug Administration clearance of the vaccine within a few weeks. The FDA will publicly debate all the evidence with its outside advisers before making a decision.
Vanderbilt's Schaffner said he expects the emergency use authorization to be granted.
AstraZeneca developed its vaccine along with scientists at Oxford University.