Health Canada said today Canadians should not be concerned about the safety of the AstraZeneca vaccine — even as a U.S. regulatory body raises concerns about the company’s clinical trial results.

Marc Berthiaume, the director of the bureau of medical science at Health Canada, said the issues flagged Monday by a U.S. federal health agency relate to the product’s published efficacy rate, not to whether it’s safe to use.

Berthiaume said Health Canada’s decision to authorize the product was not based on any of the clinical trial information U.S. authorities are now probing. He said Canada based its approval largely on data that emerged from AstraZeneca trials in the United Kingdom and Brazil, and on studies published in countries where the shot has been in use for some time.

“I think it would be alarmist to suggest that the results of additional clinical testing could lead to a change in the approval status of AstraZeneca here in Canada,” Berthiaume said.

“The additional information that was collected in the U.S. will be sent to Health Canada in the coming weeks. If there’s a need to readjust, then we’ll do that with Canadians later.”

Health Canada ‘concerned’ about vaccine hesitancy  

Dr. Supriya Sharma, Health Canada’s chief medical adviser, said U.S. questions about the efficacy rate change nothing for Canadians at this point. She conceded the barrage of headlines about the AstraZeneca shot are “something of a concern to us” because they could make some Canadians reluctant to take vaccines.

“The press and the concerns around the AstraZeneca vaccine don’t help,” she said.

WATCH: Health Canada says federal recommendations on AstraZeneca vaccine are not changing 

Sharma says federal recommendations on AstraZeneca vaccine are not changing

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In a statement released last night, the National Institute of Allergy and Infectious Diseases in the U.S. said the Data and Safety Monitoring Board (DSMB), which keeps an eye on clinical trials, found “outdated information” may have been reported by the company when it released some information yesterday.

The agency said the British-Swedish pharmaceutical giant may have released information that gives an “incomplete view of the efficacy data.”

“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,” the agency said — without stating what sort of data may have been  included improperly.

The statement came only hours after AstraZeneca released the results of its U.S.-based phase three clinical trials, which began last August and wrapped up earlier this month. Phase three is the point in a clinical trail when a vaccine maker gathers more information about safety and effectiveness and studies the effect of different doses on various groups.

The company said its COVID-19 vaccine had a 79 per cent efficacy rate for preventing symptomatic COVID-19 and was 100 per cent effective in stopping severe disease and hospitalization. Investigators said the vaccine was effective for adults of all ages, including older people — something which previous studies in other countries had failed to establish.

The product has not yet been authorized for use in the U.S.

This is just the latest public communications issue the company has faced over the last three months.

Earlier this year, a number of European countries halted vaccinations in response to questions about the product’s efficacy in people over the age of 65, only to restart them after new evidence emerged.

After Health Canada approved the shot for all adults, the National Advisory Committee on Immunization (NACI) recommended the product be used only on people under the age of 65, citing a dearth of clinical trial data on the vaccine’s effectiveness in older people.

NACI changed course last week after reviewing three “real-world studies,” saying the two-dose viral vector vaccine can and should be used on seniors.

The European Medicines Agency has also had to assure European Union member countries that the product is safe to use after reports of post-vaccine blood clots in a very small number of patients.

The agency concluded that the benefits of protecting against COVID-19 — which itself results in clotting problems — outweigh the risks.

The Public Health Agency of Canada has said it’s “possible” the vaccine may be associated with “very rare but serious cases of blood clots associated with thrombocytopenia” — a condition associated with very low levels of blood platelets. Health Canada has maintained that the benefits of the AstraZeneca COVID-19 vaccine continue to outweigh the risks.