This year’s flu vaccine only about 23% effective

By Kim Smiley

According to the Centers for Disease Control and Prevention (CDC), the flu vaccine for the 2014-2015 flu season is only about 23% effective among people of all ages.  While the flu vaccine is not perfect, the effectiveness is generally closer to 60% percent.

So what made this year different?  Why is the flu vaccine so much less effective than what has been previously observed?  The short answer is that creating a flu vaccine is not an exact science and that the experts’ best guess of which flu strains would be the most common wasn’t as good this year.

One of the reasons that a flu vaccine is needed each year while many vaccines (like the MMR vaccine) aren’t is that the flu virus changes relatively quickly.  The strains of flu that are circulating generally morph from year to year and a new vaccine is needed to protect against them.  The lag time inherent in developing a new vaccine also makes attacking this moving target  difficult.  It just takes time to develop a new vaccine that needs to be tested, manufactured and distributed to millions of people.  Companies need about six months to manufacture vaccines in the quantities required so the process of developing a new flu vaccine begins long before the predicted start of the flu season.

Every year there are hundreds of different strains of flu circulating and flu vaccines contain antigens for only 3 or 4 specific strains. Deciding which strains to include in the vaccine each year is not a simple cut and dry decision. Scientists monitor which strains of flu are circulating worldwide and use that data to select which strains to include in the vaccine, but it is difficult to predict how the virus will change months out.  The button line is that sometimes the flu virus changes unexpectedly and the vaccine ends up being less effective, as it did this year when the specific type of H3N2 virus included in the vaccine morphed after the development of the vaccine.

The question of how to prevent a similar problem in the future is tricky and doesn’t have simple answers.  There are scientists working to develop antigens that would respond to a part of the flu virus that doesn’t change, which could potentially lead to a longer lasting flu vaccine.  Until then the best way you can protect yourself is to get the flu vaccine each year. The CDC still recommends people receive the vaccine this year, even with the lower effectiveness, because it does offer some protection against the flu.

And wash your hands often with soap…that is always the simplest way to reduce the spread of disease.

To view a high level Cause Map, a visual root cause analysis, of this issue, click on “Download PDF” above.