Canada is following the lead of several European countries and suspending distribution of flu vaccine made by the pharmaceutical firm Novartis.
The decision relates to the discovery by the company of tiny clumps of virus particles in some batches of flu vaccines made at the Novartis production facility in Italy.
Health Canada, which announced the move, said Novartis has agreed to suspend distribution of its vaccines – sold in Canada as Fluad and Agriflu – while the department investigates the situation.
The department is also telling doctors and others who administer flu shots in Canada to hold off using the Novartis product for the time being.
"We think it's prudent, given the response of certain European countries to … request of Novartis – and they will be complying – to stop distributing and then to recommend to practitioners to refrain from using the (Novartis) vaccine just until this review is completed," Dr. Paul Gully, senior medical advisory for Health Canada, said Friday.
Italy, Germany and Switzerland have suspended distribution of some Novartis flu vaccine, and in the case of Germany recalled some lots of vaccine, after the clumping issue came to light.
A statement from Novartis said finding minute clumps of virus protein in vaccines is not unusual. They said their vaccines passed quality inspections and so far this year there have been no signals of adverse events associated with use of the vaccine.
"The aggregate proteins are predominantly influenza virus-derived (mainly hemagglutinin), all normal and necessary components of influenza vaccines," the company's statement said. "Aggregation of these proteins is not unusual in vaccines manufacturing."
Hemagglutinin is the protein on the outside of flu viruses that locks onto cells in the human respiratory tract to start the process of infection. Flu vaccines are designed to provoke the immune system to produce antibodies to hemagglutinin to protect against infection.
Novartis makes only about 20 per cent of Canada's annual flu vaccine purchase. GlaxoSmithKline makes the bulk of Canada's seasonal flu vaccine, though a variety of other suppliers have a share of the Canadian market.
Still, because of the way vaccine orders are placed, the hold on Novartis vaccine could put some provinces and territories in a position where they face a temporary vaccine shortfall, just at the time when flu shot programs are getting underway, Dr. Gully admitted.
He said Health Canada hopes there is a rapid resolution of the situation. But if provinces or territories have a problem with supply, efforts will be made to share across jurisdictions, he said.
Both Fluad and Agriflu are sold in single-dose formulations, pre-loaded into a syringe.
Fluad contains an adjuvant, a compound that boost the response the vaccine generates, and is licensed for use in people 65 and older.
Older adults do not mount a good response to flu vaccine and the inclusion of an adjuvant is an effort to improve the protection they get from flu shots.