Less effective flu vaccine this year could lead to more Canadian cases than usual, vaccine expert says

Looks like this season’s flu vaccine may not offer the usual amount of protection and could result in more cases with complications, especially for the elderly in both the U.S. and Canada.

Influenza A (H3N2), one of the strains covered by the current vaccine cocktail appears to have mutated, making the flu shot less effective, according to an announcement this week by the U.S. Centers for Disease Control.

And since the manufactured vaccine is the same across the entire Northern Hemisphere, it is expected that the situation will be exactly the same for Canada because we share such a long porous border, says Salah Mahmud, Director of Vaccine and Drug Evaluation Centre at University of Manitoba.

“Unfortunately, decisions on what strains to include in the vaccine have to be done by February to give the vaccine manufacturers enough time to make large amounts of doses,” Mahmud explained in an interview with Yahoo Canada News.

“So what happens is that they don’t end up working with the most recent information.”

And unfortunately, one of these components, the H3N2 virus, has changed since February. And how do we know that?

There is a medical surveillance system, called antigenic testing, that is carried out as patients present themselves with flu-like symptoms at hospitals. Samples are taken to labs to get tested and once they isolate the virus, they test the virus against antibodies from people who have already taken the vaccine. If the vaccine is effective, they will find it will kill the virus.

But this year’s testing that was carried out by the CDC found that about 50% of the isolated viruses did not react to the antibody.

“When this happens it means that the effectiveness of the antivirus will be much lower,” Mahmud said.

This partial ineffectiveness of the current vaccine is particularly worrisome with the H3N2 virus, Mahmud says, because it appears to hit the elderly hard and they typically get complications like secondary bacterial infections.

So while some of those 65 years and older may have been vaccinated, some may still end up getting sick, and that’s partly why, Mahmud believes, the CDC made the announcement this week.

“The logic of this announcement is to make sure that the general public still gets that vaccine because it will protect against the other strains, but more importantly physicians should be more alert for the possibility that the vaccine is not going to be as protective this year and get them to intervene early on to prescribe antivirals when indicative,” he explained.

And for those thinking that the vaccine may take at least a year or more to be effective, or that it may leave you more vulnerable to other viruses, Mahmud says these notions are incorrect.

"While there were some concerns raised in research studies years ago with H1N1 [Swine flu] , there has been no evidence to support these ideas,” he said.

Meanwhile, current trends and patterns for how the flu is spreading is pretty much following what we saw during last year’s influenza season. Alberta and Quebec are leading in the number of confirmed cases, according to the Public Health Agency of Canada report. And as feared with this strain, so far the largest proportion of cases have been among those over 65 years of age.

Mahmud recommends to stay the course and get the shot because it can still ease symptoms if you get the flu, and can protect from the other strains swirling around this season.