U.S. health officials have raised concerns over AstraZeneca’s COVID-19 vaccine trial, accusing the pharmaceutical giant of using outdated and potentially misleading efficacy data.

The allegations came to light early Tuesday in a written statement from the National Institute of Allergy and Infectious Diseases. The research agency said the Data and Safety Monitoring Board had notified AstraZeneca, as well as federal authorities and independent health panels, about the questionable data that showed the vaccine was 79 percent effective in preventing symptomatic coronavirus.

“The DSMB expressed concern that AstraZeneca may have included outdated information from that trial, which may have provided an incomplete view of the efficacy data,” the NIAID’s statement read. “We urge the company to work with the DSMB to review the efficacy data and ensure the most accurate, up-to-date efficacy data be made public as quickly as possible.”

According to the New York Times, the federal officials and health experts sent a two-page letter to AstraZeneca on Monday, claiming the company was selective about which data it used in its recent press release. The experts accused the company of only citing data that was the “most favorable for the study as opposed to the most recent and most complete.” The letter also stated that the vaccine’s efficacy may have been around 69 percent and 74 percent.

Dr. Anthony Fauci, the head of the NIAID, addressed the dispute during an appearance on Good Morning America.

“They got concerned and wrote a rather harsh note to [AstraZeneca] — and with a copy to me — saying that, in fact, they felt that the data that was in the press release were somewhat outdated and might in fact be misleading a bit, and wanted them to straighten it out ...” Fauci said. “It really is unfortunate that this happened. This is really what you call an unforced error because the fact is this is very likely a very good vaccine … This kind of thing does … really cast some doubt about the vaccines and maybe contribute to the hesitancy. It was not necessary.”

AstraZeneca defended its trial data in a press release Tuesday:

The numbers published yesterday were based on a pre-specified interim analysis with a data cut-off of 17 February. We have reviewed the preliminary assessment of the primary analysis and the results were consistent with the interim analysis. We are now completing the validation of the statistical analysis. 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. We intend to issue results of the primary analysis within 48 hours.