The arrival of the flu vaccine has been delayed by about one month, which means most Canadians won't have access to flu shots until mid-November.
Vaccine manufacturers usually receive small amounts of the three most common flu strains recommended by the World Health Organization, and then they grow the virus in eggs, which takes about six months. But this year, one of the strains, A/Wisconsin, was difficult to grow.
Public health experts said it would be better if the vaccine was available by mid-October to increase the time for getting people vaccinated, but flu cases don't usually peak until around Christmas time.
The delay might be a good thing, according to some experts who recommend delaying administration of the vaccine until early November so its effects last into the spring when the flu season is still active.
It takes about two weeks for the immune system to respond to the shot and build up immunity. People can still contract influenza if they get the vaccine, but it helps reduce the severity of symptoms.