AstraZeneca PLC said it would update and reissue later this week efficacy data from human trials of its Covid-19 vaccine after U.S. officials took the rare move of publicly questioning their accuracy—the latest misstep by the British drug giant as it struggles to get its shot into American arms.
In an early-morning statement, the National Institute of Allergy and Infectious Diseases said it had been informed by the independent data-monitoring board working with AstraZeneca on the U.S. trials that the drug company might have used out-of-date information in its public disclosure of the vaccine’s effectiveness. The day before, AstraZeneca released interim data from a large-scale U.S. trial that it said found its Covid-19 vaccine to be 79% effective in preventing symptomatic disease.
The results served as a short-lived vote of confidence in the shot, which has been clouded by uncertainty over previous, confusing efficacy results and large-scale production problems. More recently, reported cases of rare blood clotting in Europe raised concerns about the vaccine’s safety, though European regulators found no link between the clots and the drug, and have recommended its continued use. The U.S. trials showed no link between the clotting and the vaccine, and the NIAID statement Tuesday didn’t raise questions about that finding or other safety-related issues.
“Any type of thing like this could unfortunately contribute to a lack of confidence in the process,” said Dr. Anthony S. Fauci, the nation’s leading infectious-disease expert. Fears that the vaccine might trigger rare, but serious, side effects had led more than a dozen countries, mostly in Europe, to temporarily suspend the use of the shot, European regulators last week affirmed the vaccine’s safety. The results from the U.S. trial on Monday — providing the cleanest, most complete picture of the vaccine’s efficacy — seemed to validate the vaccine’s safety and made it look more effective than in earlier trials.
In short, it bolstered the credibility of arguably the world’s most important vaccine, one that has been authorized for use in more than 70 countries. But the overnight announcement from the institute immediately raised a new set of questions about it and AstraZeneca. “If they keep making these unforced errors, then that’s going to derail confidence, and that will really affect our ability to combat this pandemic,” said Dr. Peter J. Hotez, a vaccine expert at the Baylor College of Medicine.