Vaccine success rate not yet known this year, but flu shot is important: public health

By Tyson Nayler

BELLEVILLE – This year’s flu season in Ontario could be more severe than average due to an ineffective vaccine, according to media reports.

Each year a new influenza vaccine is developed to match the prominent strain of virus that is in effect. The strain will often change each year and doctors have to be able to properly determine which vaccine they will provide the public to get immunized. Bill Sherlock, a program manager for vaccine, preventable disease and communicable disease at Hastings Prince Edward Public Health, says that this winter’s strain is H3N2, a virus that is more severe than H1N1, which is a more common type of flu.

“What usually happens is the strain will change from year to year and you either get a strain that’s H1N1 or H3N2 – and even within these strains there are different variations within the virus,” Sherlock said.

The vaccine used in Ontario is developed based on the flu strain that is circulating in the southern hemisphere, where the virus hits first each year, during the winter that happens there while we’re enjoying summer. Sherlock noted that the media reports suggesting an ineffective vaccine are based on a poor experience in the southern hemisphere this past year, and added, “That does not necessarily translate to the northern hemisphere.”

On average, the effectiveness for a flu vaccine varies anywhere between 40 and 60 per cent, Sherlock said. Some years, if the vaccines don’t match the flu strain, it can be as low as 10 per cent, he said.

“We may indeed end up with a poor influenza vaccine – but we don’t know that for certain for a few more months.”

In the meantime, it’s important for everyone to get vaccinated, Sherlock said, especially those in retirement and long-term-care homes, who tend to be hit hardest by the flu.

“It’s the same as every year, really; you offer the vaccine and encourage the general public to get it. We distribute it to the long-term-care homes, retirement homes, and generally they are good for getting their residents immunized. Usually a little more than 90 per cent get the vaccine.”

Sherlock says there has been an increase this year in demand to be immunized. The Public Health Agency of Canada estimates that approximately 35 per cent of the population gets the flu shot, and this year, Sherlock says, that there has been a 30 to 35 per cent increase for pharmacies in the Hastings-Prince Edward region.

The main concern for public health – no matter how severe the strain of flu is – is adults 65 years and older, children five years and younger and also those who are in compromised conditions, he said – and the best way to protect them is with the flu shot.