A safety board that oversaw the US clinical trial of a COVID-19 vaccine from AstraZeneca warned on Tuesday that results released by the Anglo-Swedish drugmaker may have included "outdated and potentially misleading" data.

In response, AstraZeneca said it would publish up-to-date results from its latest vaccine trial within 48 hours. The results that were questioned had been released on Monday.

In a rare move, the National Institute of Allergy and Infectious Diseases, or NIAID, said in a statement that the Data and Safety Monitoring Board, or DSMB, which monitored the AstraZeneca vaccine trial, is concerned that the trial result may have included outdated information.

If the company did include such information, it "may have provided an incomplete view of the efficacy data", the NIAID said in the statement.

The DSMB, an independent group of health experts appointed by the National Institutes of Health to review clinical studies, also notified other federal health agencies and AstraZeneca of its concerns, according to National Public Radio.

AstraZeneca, in a statement released on Tuesday, said the data it released on Monday included cases up to Feb 17.

"We will immediately engage with the independent data safety monitoring board 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," the drugmaker said.

The company, based in Cambridge, England, said it had reviewed the preliminary assessment of its full, or primary analysis, and the results were consistent with the interim analysis. The company is now completing the validation of the statistical analysis.

AstraZeneca reported on Monday that its vaccine is 79 percent effective against symptomatic COVID-19 and has 100 percent efficacy against severe or critical disease.

The trial confusion comes after some European countries suspended the vaccine last week after reports of a handful of recipients reporting blood clots. Vaccinations have resumed in a number of the European nations which halted the jabs.

Export controls

Separately, the European Union's executive body said on Wednesday that it has a plan to guarantee that more jabs produced in the bloc are available for EU citizens before they can be shipped for exports.

Brussels has been infuriated that Britain has laid claim to vaccines produced at a plant in the Netherlands by AstraZeneca at a time when the UK-based firm has fallen short on deliveries promised to the EU.

EU guidelines on restricting vaccine exports have already been used once to prevent an AstraZeneca shipment leaving Italy for Australia.

The draft of the updated rule complains of countries preventing exports to the EU "either by law or through contractual or other arrangements concluded with vaccine manufacturers".

In France, authorities said on Tuesday they were investigating the death of a 26-year-old medical student days after he received the AstraZeneca vaccine.

The student died on March 18 in the western city of Nantes, 10 days after receiving the jab.

Also on Tuesday, Russian President Vladimir Putin was vaccinated out of sight of the cameras, his spokesman said.

Dmitry Peskov had said earlier that the president would get the vaccine out of the public eye because "when it comes to getting vaccinated on camera, he has never supported that".

Minlu Zhang in New York and agencies contributed to this story.