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CDC: Flu Vaccine Not Very Effective This Season

By Brenda Goodman, MA
WebMD Health News

Reviewed by Hansa D. Bhargava, MD

Jan. 15, 2015 -- It's official. This season's flu vaccine is less effective than experts had hoped.

New research by the CDC shows that this batch of flu shots cuts the risk of needing medical treatment for flu symptoms by about 23% on average. Compared to past seasons, that's on the low side. Since the CDC started measuring how well flu vaccines work in 2005, their effectiveness has ranged from 10% to 60%.

Experts say it's still a good idea to get the flu shot, even though protection from the current vaccine is spotty.

"It's always better to have some protection rather than no protection," says Len Horovitz, MD, a lung specialist at Lenox Hill Hospital in New York City. "Why would you opt for zero, even if the best you could do is 15% or 20%?"

Horovitz sometimes encourages his patients, many of whom are at high risk for complications from the flu because of lung problems like asthma or COPD, to get the shot twice -- once early in the season and again 5 to 6 months later.

The idea -- which hasn't been scientifically proven and is not endorsed by the CDC -- is that the second shot might work like a booster to revive flagging immunity. Horovitz thinks that might be important for older adults and those with underlying medical conditions, who tend to have a poor response to vaccines in the first place.

"It's a little bit controversial," he admits. "I'm recommending it to people at high risk who were vaccinated in August or September, which was a while ago."

Coverage Gap

During years when the vaccine is a good match for the flu virus strains that are making people sick, effectiveness is around 50%-60%. And it's been in that range for the past four seasons.

But nearly three-quarters of the viruses that are making people sick this year are different than the strains included in the vaccine's formula. That means people aren't getting as much protection from the shot.

The CDC acknowledged the coverage gap last month, and last week the agency urged doctors and other health care providers to act quickly to prescribe antivirals -- certain kinds of flu-fighting medications -- if they suspect the infection.

How well flu vaccines work also varies by age. In general, older children and healthy younger adults get the most protection from the shots, because their immune systems are mature and working at their peak. Vaccines are less effective in young children and the elderly.

Based on early estimates, the CDC says this season, the vaccine appears to cut the risk of a doctor's visit for the circulating H3N2 flu viruses by 26% in school-aged children, by 12% in adults ages 18 to 49, and by 14% for people 50 and over.

But getting vaccinated is "still the best thing you can do to prevent the flu," says Seth Podolsky, MD. He's an emergency medicine specialist at The Cleveland Clinic in Ohio.

"Just because the strains that are going around right now may not be a part of the vaccine, the strains that come around later in the season may very well be," he says.

Be sure to wash your hands often, and stay home if you're sick.

For those who are unlucky enough to come down with the flu's telltale fever and body aches, Podolsky says urgency is key.

"If you are having significant symptoms, you want to get in touch with your doctor as soon as possible so that, potentially, antiviral medications can be prescribed. They're most effective when given within the first 48 hours of having symptoms," he says.

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SOURCES: CDC: Morbidity and Mortality Weekly Report, Jan. 16, 2015. Len Horovitz, MD, Pulmonologist, Lenox Hill Hospital, New York, N.Y. Seth Podolsky, MD, vice chairman, emergency medicine, The Cleveland Clinic, Cleveland, Ohio.

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