New York, Mar 23 (IANS): US-based National Institute of Allergy and Infectious Diseases (NIAID) expressed concern on Tuesday that British-Swedish pharmaceutical major AstraZeneca may have provided outdated information on the efficacy data related to the clinical trial of its Covid-19 vaccine, which may have provided an incomplete view of the efficacy data.

On Monday, the drug maker showed that its vaccine's efficacy is 79 per cent in preventing symptomatic illness in a large trial in the US.

However, in an unusual statement, the independent Data and Safety Monitoring Board (DSMB), which reviewed the trial results, notified NIAID, Biomedical Advanced Research and Development Authority (BARDA), and AstraZeneca that it is concerned over the information released by AstraZeneca on the initial data from the clinical trial of its Covid-19 vaccine.

"We urge the company to work with the DSMB to review the efficacy data and ensure that the most accurate, up-to-date efficacy data is made public as quickly as possible," the US-based agency said.

"Authorisation and guidelines for use of the vaccine in the US will be determined by the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) after a thorough review of the data by independent advisory committees," it added.

Earlier, the Phase III AstraZeneca trials in the US showed an efficacy of 80 per cent in people over the age of 65, the most vulnerable group for contracting Covid-19 with deadly consequences. Twenty per cent of the trial participants were over the age of 65.

The vaccine, known by the scientific name 'AZD1222', was 100 per cent effective in preventing hospitalisation, the company had said in a statement. It means that even those who contracted Covid-19 after vaccination had only less severe symptoms and did not need intensive treatment in a hospital.

Initially, the DSMB conducted a specific review of thrombotic events, as well as cerebral venous sinus thrombosis (CVST), which refers to the presence of a blood clot in the dural venous sinuses, with the assistance of an independent neurologist.

The board found no increased risk of thrombosis or events characterised by thrombosis among the 21,583 participants receiving at least one dose of the vaccine.

The specific search for cerebral venous sinus thrombosis found no events in this trial, AstraZeneca said, adding that vaccine efficacy was consistent across ethnicity and age.