Why Doesn't the Influenza Vaccine Work for More than One Year?

Paul A. Offit, MD, explains that because different strains of the influenza virus circulate every year, immunization one year doesn’t protect against the disease the following year, and that’s why a yearly dose of the vaccine is recommended.


Why doesn't the influenza vaccine work for more than one year?

Paul Offit, MD:  Hi, my name is Paul Offit, and I’m talking to you today from the Vaccine Education Center here at The Children’s Hospital of Philadelphia. One question that parents ask, reasonably, and frankly all adults, is, “Why do I have to get the influenza vaccine every year? I mean, usually if I just have gotten two doses of measles-containing vaccine, or mumps-containing vaccine, or German measles, or chickenpox, that’s it, I’m done with it. Why do I have to keep getting an influenza vaccine?”

And the reason is, and what makes influenza virus particularly evil, is that the virus is able to mutate, or change its surface, every year so much so that immunization or natural infection one year doesn’t protect against the disease the following year. Which is to say, different strains circulate every year. And for that reason, pharmaceutical companies have to try and figure out which strains are going to be circulating next year. And essentially make a new influenza vaccine every year.

If influenza vaccine were composed of only a single serotype, probably one vaccine could protect for a long period of time. But that’s not the case. And so right now researchers are trying to find a way to find those common components of all influenza viruses that one can then put into vaccine to allow vaccines to be given certainly far less frequently. But for now, that hasn’t happened.

Thank you.

Related Centers and Programs: Vaccine Education Center

Last Reviewed on Apr 23, 2015