AstraZeneca (AZN  ) has revised its coronavirus vaccine's efficacy rating after being rebuked by the National Institute of Allergy and Infectious Diseases (NIAID). The debacle is just the latest for AstraZeneca, which has faced numerous consecutive blunders in testing its vaccine.

After releasing the results of its phase three clinical trial on Monday, AstraZeneca was blindsided on Tuesday by a statement from the NIAID, which alleged that the company based its trial results on old data. According to the NIAID, data that had been viewed by the trial's Data and Safety Monitoring Board initially indicated an efficacy rate of between 69% and 74%, considerably lower than AstraZeneca's reported rate of 79%. The company has since revised its efficacy rate to 76%.

The news prompted immediate backlash, with many U.S. officials lobbying criticism at the company and accusing it of manipulating data. Dr. Anthony Fauci remarked that the incident was likely an "unforced error" and stated that he still believed that the vaccine was likely still safe to use. "This kind of thing does...really cast some doubt about the vaccines and maybe contribute to the hesitancy. It was not necessary," Fauci said, quoted by CNBC.

To make matters worse, AstraZeneca is also facing increasing pressure from the European Union, with an AstraZeneca plant being inspected by Italian authorities on Saturday at the E.U.'s request. The inspection was the latest event of an ongoing saga of alleged deceit by AstraZeneca. The E.U. has accused of misleading the public over its capability to deliver its promised 120 million doses.

The increasingly embattled firm has been under fire consistently since September when AstraZeneca failed to report the suspension of its clinical trial to the Food and Drug Administration. The company also faced accusations of giving trial participants the wrong doses.

The week began strong for AstraZeneca, thanks to the ostensibly good news of its 79% efficacy rate, which drove shares up 4% during trading on Monday, reaching $51.20 after starting the day at $49.20 After the NIAID issued its statement on Tuesday, shares tumbled 3.5% to $49.39. Shares fell an additional 1.2% on Wednesday, sliding to $48.79.