The flu is back and the news is bad. The Centers for Disease Control and Prevention (CDC) says that its primary strategy, vaccination, may not work very well this year.
Bad Guess
Every year health officials have to anticipate which strains of influenza virus will predominate. That guess needs to be made months before people start suffering with fever, cough, congestion, aches, pains and other symptoms of flu.
This year, the vaccine is not a good match for the viruses that are circulating. Between the time that production began and people started getting sick, flu viruses changed enough that the shot will at best protect against half of the viruses out there.
How Helpful Is the Flu Shot?
Even when there is a good match, the vaccine is not as helpful as many imagine. The CDC’s evaluation of 2013-2014 flu season revealed that the vaccine was less than 40 percent effective among older people (MMWR, Dec 12, 2014). Since older adults are especially susceptible to complications of influenza, it is disheartening to learn that even a flu shot that is well matched doesn’t always protect them.
Michael Osterholm, PhD, MPH, director of the Center for Infectious Disease Research and Policy at the University of Minnesota told Minnesota Public Radio
“The concept of how well vaccines protect against flu viruses is much, much more complicated than just a simple match…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.”
According to Dr. Osterholm and his colleagues, “Evidence for consistent high-level protection is elusive for the present generation of vaccines, especially in individuals at risk of medical complications or those 65 years old or older.” (CIDRAP, Oct. 2012)
Two years ago the vaccine was an excellent match, with 92 percent of the circulating flu viruses covered. But the post-season flu analysis showed that the flu shot was only about 27 percent effective for people over 65. Worse, in this age group it was only 9 percent effective against the most virulent virus, H3N2 (the one that is causing havoc this year).
Evidence-Based Public Health
Health experts like to claim that they practice evidence-based medicine. In other words, there is solid science behind their treatment strategies.
But the CDC, while acknowledging that this year’s vaccine is not a good match, is still urging everyone to get a flu shot. The reason: even if it won’t prevent illness, it might make symptoms less severe. We wish there were better data to support this belief.
The CDC is also recommending that doctors prescribe antiviral medicines for people who come down with symptoms of influenza. Oseltamivir (Tamiflu) and zanamivir (Relenza) can both be used to reduce the duration of flu illness, but they work better if taken as early as possible after symptoms begin, ideally within less than 48 hours. There is more information on how to manage flu symptoms in our Guide to Colds, Coughs and the Flu.
