This year’s flu shot may not be the right match, CDC tells doctors

WATCH: Flu shot may not protect you against this season’s strain says CDC. Omar Villafranca reports

PARIS – If you rolled up your sleeves for this year’s flu shot, you might not be fully protected, the Centers for Disease Control and Prevention is warning.

In an advisory to American doctors, the CDC says that the flu vaccine may not work against the most common strain of flu that’s making its way through the U.S.

The flu vaccine typically protects against three strains. This year, North American doctors braced for a strain of H1N1 called A/California/7/2009, an H3N2 strain called A/Texas/50/2012 and an influenza B similar to a B/Massachusetts/2012.

H3N2 appears to be infecting most Americans, but the trouble is that it’s mutated and the CDC suggests that only half of the people vaccinated were protected from the flu.

This isn’t uncommon. Each year, strains of the influenzas mutate and re-emerge, infecting victims and triggering a new season. Those of us in the northern hemisphere keep a watchful eye over the flu in the southern hemisphere, which affects residents during their winter (or our summer).

READ MORE: 5 ways to protect yourself from the flu

Picking out three strains for a vaccine is guesswork, and by the time influenza makes its way into the northern hemisphere, it’s had time to mutate or “drift.” But by then, the flu vaccine is already formulated.

The CDC is still urging doctors to keep vaccinating and for patients to get their flu shots, though. While it may not protect against this one strain of the flu, it’ll still fight against other strains floating around. It’ll also lessen the risk of complications.

“Though reduced, the cross-protection might reduce the likelihood of severe outcomes such as hospitalization and death,” the CDC advisory said to American doctors, according to U.S. reports.

READ MORE: Is enterovirus more concerning than the flu? What parents need to know

“In addition vaccination will offer protection against circulating influenza strains that have not undergone significant antigenic drift from the vaccine viruses (such as influenza A (H1N1) and B viruses).”

Alberta Health says the vaccine is adjusted to address the potential strains that might be making their way into Canada.

“We are reviewing the CDC’s report and are currently monitoring the situation,” Carolyn Ziegler, Alberta Health spokeswoman, said in an email to Global News.

The flu season typically arrives in November and lingers until March. It’s slowly trickled into Canada already.

“Based on what we saw in the southern hemisphere, we should expect a moderate influenza season and we shouldn’t be seeing any significant problems,” according to Dr. Gerald Evans.

Evans is a Queen’s University medicine professor and chief of infectious diseases at Kingston General Hospital.

READ MORE: What to expect from this year’s flu season

“There’s no indication that we’re in for a bad flu season,” he said. But that still means that thousands of Canadians will be hospitalized for their symptoms and complications, he cautioned.

At this point, Evans says that vaccination rates nationally sit at a meagre 20 to 25 per cent while health care workers report higher numbers at about 40 per cent.

Evans says that if at least 75 per cent of the public were to be immunized, “herd immunity” would occur. That means that even if a single person wasn’t vaccinated, if most of the people around them were, the risk of transmission would be very low.

He cautions that while most of us feel healthy, the flu shot has benefits that extend beyond our own immune systems.

“I’m a doctor and I get my shot every year so the likelihood of me getting the flu is reduced, and that means I’m unlikely to transmit to my family, my friends and to my patients that I see,” he said.

“It’s one of those things where it’s good for you, but it’s also good for everybody around you too.”

READ MORE: Flu shot halves risk of heart attack or stroke in heart disease patients, Canadian study suggests

Kids as young as six months old can start getting the vaccine.

It’s also recommended for populations at risk of complications. These people who are more vulnerable include pregnant women, children under five years old, seniors and residents in long-term care or nursing homes.

Those with underlying health problems, such as chronic diseases (asthma, chronic bronchitis, cancer) should also make their way to a flu vaccination clinic.

Evans suggests that getting the vaccine earlier helps. It takes about two weeks for the vaccine to be most effective, and its effects are long-lasting.

READ MORE: Flu shot halves risk of heart attack or stroke in heart disease patients, Canadian study suggests

For more on the flu season, take a look at the government’s Flu Watch.

To read about flu prevention tips, take a look at the Public Health Agency of Canada’s website.

carmen.chai@globalnews.ca
Follow @Carmen_Chai