The curious case involving the AstraZeneca-Oxford University Covid-19 vaccine took a new turn this week, with Canada suspending the vaccine for those younger than 55 years due to the risk of rare blood clots being reported out of Europe.

And from Wednesday, Germany too restricted its use to 60 year-olds and above, according to reports from Berlin.

The Canadian directive followed a recommendation from the National Advisory Committee on Immunization. Pointing to "substantial uncertainty" on the benefits of the vaccine, a report from Toronto quoted Dr Shelley Deeks, vice-chair of the Committee as saying, the updated recommendations follow new European data that suggests the risk of blood clots was "potentially as high as one in 100,000, much higher than the one in one million risk believed before."

Finland, too has reportedly resumed its vaccination, but only in those above 65 years. Finland was among the 10-odd countries, including Norway, Sweden and Denmark, who stopped using the vaccine following reports of rare blood clots in vaccine recipients.

However, some of these countries have resumed the Oxford-AZ vaccine after the European Medicines Agency, the UK regulator and the World Health Organization weighed in on the vaccine's benefits over its risk. All three agencies did, however, caution on the rare blood clots and in younger people.

The Oxford-AZ vaccine is made and supplied in India through Serum Institute, and it is one of the vaccines being rolled out in the country along with the Bharat Biotech one. However, health authorities have not, to date, flagged concerns on incidents of rare blood clots.

Additional assessments

On Monday, Health Canada said it would be issuing "additional terms and conditions on the authorizations of the AstraZeneca and Verity Pharmaceuticals/Serum Institute of India vaccines."

This would include a requirement that manufacturers conduct a detailed assessment of the vaccine's benefits and risks by age and sex in the Canadian context. "This information will support the ongoing evaluation of these rare blood clotting events and allow Health Canada to determine if there are specific groups of people who may be at higher risk," it added.

Recently the regulator had communicated to its people on assessing very rare adverse events reported in Europe of thrombosis (blood clots) with thrombocytopenia (low blood platelets) occurring after immunization with the AstraZeneca vaccine. "The product information was recently updated to reflect this information," the authority said.

Evidence demonstrates effectiveness

In its response, AstraZeneca told BusinessLine, that regulatory authorities in the UK, European Union and the WHO had concluded that the benefits of the vaccine significantly outweighed the risks "across all adult age groups."

Further, it added, "Tens of millions of people have now received our vaccine across the globe. The extensive body of data from two large clinical datasets and real-world evidence demonstrates its effectiveness, reaffirming the role the vaccine can play during this public health crisis."

"Health Canada's guidance issued to Canadian healthcare practitioners last week remains unchanged and provides vaccine recipients with information on the signs and symptoms to monitor for the following vaccination," it pointed out.