Editor’s Note: On March 25, AstraZeneca updated its data to say that their coronavirus vaccine is 76% effective against symptomatic COVID-19.
An independent group of medical experts in the U.S. has raised concerns that AstraZeneca may have released "outdated" data on its COVID-19 vaccine.
AstraZeneca announced on Monday (March 22) that its coronavirus vaccine was 79% effective at preventing symptomatic COVID-19 and 100% effective at preventing severe or critical illness and hospitalization in a late-stage trial conducted in the U.S. that involved more than 32,000 volunteers.
Later that day, the Data Safety and Monitoring Board (DSMB), an independent group of experts that analyzes study data, alerted the National Institutes of Allergy and Infectious Diseases (NIAID), AstraZeneca and the Biomedical Advanced Research and Development Authority (BARDA) that the company may have included outdated information. And if the data is indeed outdated, it "may have provided an incomplete view of the efficacy data," according to a statement from the NIAID posted on Tuesday (March 23).
Related: Quick guide: COVID-19 vaccines in use and how they work
The NIAID urged the company to work with the data and safety monitoring board to "review the efficacy data and ensure the most accurate, up-to-date efficacy data be made public as quickly as possible." On Tuesday, AstraZeneca released a statement in response to NIAID saying that the numbers they released in a press release on Monday were based on a "pre-specified" interim analysis that had a data cutoff of Feb. 17. (An interim analysis is a preliminary analysis that analyzes data from an ongoing trial before that trial is completed.)
"We have reviewed the preliminary assessment of the primary analysis and the results were consistent with the interim analysis," they wrote. "We will immediately engage with the independent data safety monitoring board (DSMB) to share our primary analysis with the most up to date efficacy data." They added that they intend to issue the results of the primary analysis within 48 hours.
The AstraZeneca vaccine has not yet been approved for emergency use in the U.S., but it has been approved in various other countries.
The company's COVID-19 vaccine has come under scrutiny after a number of countries in Europe, including Germany, France, Italy and Spain, stopped or paused the AstraZeneca vaccine rollout over concerns of potential links to blood clots.
After an investigation, the European Union's European Medicines Agency concluded on March 18 that the AstraZeneca vaccine is safe and effective, even though the rare risk of blood clots could not be completely ruled out, Live Science previously reported.
Originally published on Live Science.