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A public health message about flu is generating debate about the effectiveness of the vaccine.


The Centers for Disease Control warned earlier this month that this year's flu vaccine could provide less protection than usual against the H3N2 subtype of influenza A that is circulating widely. That led some flu experts to say that the message is confusing.

Although the vaccine is not well matched against the dominant strain of the flu this year, it still could protect people, said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.


"The concept of how well vaccines protect against flu viruses is much, much more complicated than just a simple match, Osterholm said. "I'm surprised that CDC continues putting emphasis on this."

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 that found no consistent correlation between the vaccine's effectiveness and how well it was matched to circulating viruses.


"We had very bad matches and the vaccine performed as we would expect on an average basis and we've had years where there's been a really good match and the vaccine provided little to no protection," he said.


Osterholm said public health officials have been slow to acknowledge this uncertainty in their recommendations that people get the flu vaccine. That has hurt the quest to develop a better, more reliable vaccine, he said.
If the public has the impression that the current vaccine is good enough, he said, there's little incentive for investors to risk $1 billion to develop a better one.


The CDC still recommends vaccination as the best defense against flu. Included in the agency's 

 was the suggestion that even if the vaccine failed to prevent an individual from contracting flu, it might help reduce a person's flu symptoms. 


Osterholm said his research team and others have found no strong evidence to support that idea either.


"I still say get your flu shot, it's the best tool that we have," he said. "But we should be doing it on the best data we have and there just is no comprehensive, compelling data that says when you get your flu shot that it even reduces the severity of illness or hospitalization."


Edward Belongia, an epidemiologist at the Marshfield Clinic Research Foundation in Wisconsin, said health officials do not yet understand why the flu vaccine works as expected some years and not as well in other years.


But he said large mismatches between the vaccine and the virus virtually assure that the vaccine won't work well.


After analyzing the genetic changes in some of this season's H3N2 viruses, Belongia concluded that CDC officials are justifiably worried that the vaccine may not be effective against that strain.


"This is a pretty substantial difference on these viruses," he said. "So I think it's justified to be concerned about it. But it's true that we don't exactly know what the vaccine effectiveness is going to be."


Belongia thinks there's value in pointing out the limits of the flu vaccine. But he also worries that the public will wrongly get the impression that the vaccine doesn't work at all and isn't worth bothering with.


Karen Martin, an epidemiologist at the Minnesota Department of Health, shares those concerns.


 
"I can tell you that messaging has been very confusing and as new data becomes available, sometimes it's difficult to synthesize all of that and to get the right message out to the public," she said.


Martin said the health department stands behind its message that people should get vaccinated against flu, even if protection against the predominant virus circulating this season isn't guaranteed.


But she said the agency is also putting a lot more emphasis on other ways to prevent flu from spreading. Those tools include diligent hand-washing and reminders to cover coughs.


Health officials are also urging doctors to make more use of antiviral medications that can lessen flu symptoms and shorten the duration of illness.


"I think that we all can agree that there are some tools that we have and since none of them are 100 percent, we should really use all of them," Martin said.

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The Centers for Disease Control has warned that this year's vaccine could provide less protection than usual against the H3N2 subtype of influenza A that is circulating widely. Some flu experts say that message is confusing.

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