Aileen M. Marty, M.D.

Director, FIU Health Travel Medicine Program and Vaccine Clinic

We may be in for a nasty flu season, and getting a flu shot may help, but not as much as was hoped. The Centers for Disease Control (CDC) is warning that this year’s flu vaccine is less effective because among the flu viruses circulating this season, the most commonly detected virus has mutated. "We could have a season that is more severe than most with more hospitalizations and more deaths," said Dr. Tom Frieden, director of the CDC. Influenza kills an average of 20,000 Americans every year. Already, five children are known to have died from flu-related illnesses this season. We tend to think of the flu vaccine as one thing, but it’s not that simple. It’s impossible to predict with certainty which flu viruses will predominate during a flu season; so a panel of experts tries to predict which three of the thousands of strains of flu are most likely to cause trouble any given year and these are combined into what’s called a trivalent vaccine. In this year’s trivalent vaccine, they chose to target the following Influenza A viruses: H1N1, and H3N2 and one strain of Influenza B virus.

Why vaccine is less effective

Well, they got two out of the three right. As it turns out, more than half of the flu cases studied by the CDC so far this season were caused by an H3N2 strain that has “drifted”, or changed from the type targeted by this year’s flu vaccine, making it less effective against that strain.

To skip or not to skip vaccine?

Still, the CDC and other experts recommend getting a flu shot. The effectiveness of the vaccine against the virus may not be quite as good, but it is still better than no protection. Vaccination against one flu virus can provide protection against different but related viruses, and can also make your illness milder if you do get sick; which in turn reduces the risk of complications.

If you get the flu

Because the vaccine is not as accurate at targeting one the three key flu strains circulating this year, it is extremely important that if you do get sick, you start taking antiviral medication as early as possible. Anti-viral drugs like Tamiflu and Relenza that work against the flu virus, only really work if they are given within 48 hours of your becoming sick; so it is crucial that as soon as you start feeling flu symptoms: fever, sore throat, cough, body aches; you see a doctor.