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This year's flu shot missing new strains of virus

Updated Wed. Oct. 24 2007 9:57 PM ET

CTV.ca News Staff

Canadians heading out to get their annual flu shot may want to know that the strains of the influenza aiming for North America appear to be drifting and mutating, raising questions about how much protection this year's flu vaccine will offer.

The process of creating the annual flu shot is a complicated one and actually begins almost a year ahead of time.

The World Health Organization monitors flu activity around the world, looking for predominant strains.

As flu viruses reproduce, they often trigger slight changes in their genetic code, which scientists call antigenic drift.

The WHO researchers take particular note of what's happening in the southern hemisphere to see what strains are emerging there, since they go through their winter flu season long before we do.

The WHO then selects the strains that they think are most likely to predominate in the northern hemisphere. They generally select three -- two subtypes of influenza A viruses and one influenza B virus-- to go into the vaccines to be used the following fall and winter.

Each year, authorities change one or two of the three strains in the vaccine, which is why it is important to get a new flu shot every year to ensure protection against the most recent strains.

This year's supply of shots is already being sent out to clinics and doctor's offices across Canada. But experts say it's beginning to appear that this year's vaccine may have two relative mismatches -- two viruses have been changing and may no longer match the viruses contained in this year's vaccine.

And because it takes at least six months to manufacture the vaccines, it's far too late to change them.

This year, scientists picked these three strains:

Influenza A - Solomon Islands/3/2006 (H1N1)-like
Influenza A - Wisconsin/67/2005 (H3N2)-like
Influenza B - Malaysia/2506/2004-like antigen
The Wisconsin strain, says the Public Health Agency of Canada, has already mutated into a different form than the one used for the vaccine, and the Malaysia strain shows signs of changing too.

"There is an inherent vulnerability in trying to develop a vaccine now for what might happen six months from now when flu season starts," says infectious disease specialist Dr. Neil Rau. "And with a strain mutating or gradually mutating, sometimes the guess is good, sometimes the guess is sub-optimal and sometimes it's bad."

"The process of making the vaccination is something of an educated guess based on what happened in the southern hemisphere during the preceding season."

No one knows how severe this year's flu season will be but Rau says it's theoretically possible the mismatch could result in more flu illnesses and hospitalizations.

"The worst case scenario with a bad match situation would be lot of disease in the elderly, manifesting in nursing home and cruise ships outbreaks, and with children you might see a lot of absenteeism and therefore a lot of parents off work as a result trying to care for them," he says.

Flu bug 'drift' speeding up


But other experts say these viral drifts are not unusual and happen on a regular basis because of the dynamic nature of the flu virus. They also note that in the past five years, the flu bugs have been drifting faster, though no one is sure why.

"We have noticed that there have been, certainly in one of the influenza A subtypes more recently, more frequent or rapid change in the virus, more rapid evolution," says Danuta Skowronski of the epidemiology services branch of the B.C. Centre for Disease Control.

"Having said that, though, that more rapid evolution has not been associated with more severe or intense outbreaks, so how meaningful that is ultimately is uncertain."

"It certainly makes it more difficult in terms of keeping pace with the changes in the vaccine to match those changes in the virus," she says. "But in terms of overall illness impact in the community, we have not seen that that has increased."

No drug or vaccine is ever 100 per cent effective and this year's vaccine won't be a perfect match either. But scientists point out that the antibodies the vaccine helps produce will offer some immunity over whatever strains do arrive.

"In recent seasons, even where there has been a vaccine mismatch, the vaccine can afford 40-50 per cent protection," says Dr. Theresa Tam of the Public Health Agency of Canada.

And some protection is better than none, especially for the elderly, she says, for whom the flu can actually be fatal.

"Even if it doesn't protect you from actually getting it, it can reduce the severity of the illness and complications," she notes.

That's why public health experts say, despite the complex science of tracking drifting strains, the flu vaccine is still the best protection against a tricky disease.

Influenza and pneumonia killed 4,725 Canadian in 2002, the last year for which detailed statistics are available, according to Statistics Canada. The National Advisory Committee on Immunization recommends that everyone over the age of six months be vaccinated against the flu.

With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip
 

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A Flu shot

Me having a flu shot. Never had one or one of late. I guess that we are isolated in australia. Or are we. :rolleyes: :confused:
 

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Discussion Starter · #3 ·
I didn't get my first Flu shot until 2006.

I just didn't want one or feel I needed one. In 2003, I had to cut my Christmas vacation short since I had caught the Bad Flu and literally thought I was going to die. I had to sit up ALL the time since my lungs had been invaded by congestion so bad which I couldn't get rid of no matter what medicine I used. I could barely breathe. My sugars were high. I couldn't eat anything because I felt nausea. I've been through many Bad things that I managed to endure but I do know when it's time to ask for assistance.

My Family and I returned to our residence so I could be near my Hospital...... You know....in case I croaked...:D...where I received Medical assistance.

Being that we have a Life-threatening disease, it is important to have the upper hand when it comes to our health. Especially when we get to middle-age. There a lot of bad stuff out there that can kill us.

You live in Australia Peter....not in a cave. ;)
 

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