Pharmaceutical company AstraZeneca may have released outdated information in the “initial data from its Covid-19 vaccine clinical trial”, the United States’ National Institute for Allergy and Infectious Diseases said in a statement on Tuesday.

The development came a day after AstraZeneca announced that advanced trial data from a study in the United States showed that its coronavirus vaccine was 79% effective in preventing symptomatic cases and 100% effective in preventing severity and hospitalisation.

The American medical body said that the Data and Safety Monitoring Board had expressed concern about the matter and also raised it with the Biomedical Advanced Research and Development Authority and AstraZeneca.

“The DSMB expressed concern that AstraZeneca may have included outdated information from that trial, which may have provided an incomplete view of the efficacy data,” the NIAID statement said. AstraZeneca has now been asked by the agency to review the efficacy data provided by it earlier and “ensure the most accurate, up-to-date efficacy data be made public as quickly as possible”.

US infectious diseases expert Anthony Fauci heads the NIAID. He is also a part of the National Institutes of Health. The role of the DSMB is to provide study oversight and evaluate clinical data to ensure safe and ethical conduct of trials, according to Reuters.

Doubts were cast on the AstraZeneca vaccine after many European countries suspended its use following reports of unusual blood clots in vaccine recipients. However, after the European Medicines Agency said the jab was “safe and effective”, many countries restarted its use.

Countries that suspended the use include Denmark, Norway, Iceland, Germany, France, Italy, Ireland, Bulgaria, The Netherlands, Austria, Estonia, Latvia, Lithuania and Luxembourg.

In spite of the late-stage human trials results announced on Monday, the vaccine is yet to receive authorisation for use in the US. AstraZeneca needs to submit its findings to the US Food and Drug Administration. An FDA advisory committee will then publicly debate the evidence submitted before deciding whether to allow its emergency use.

In India, the AstraZeneca-Oxford vaccine is one of the two vaccines approved for emergency use. Covaxin, developed by Bharat Biotech in collaboration with the Indian Council of Medical Research and the National Institute of Virology, is the other vaccine.