Why is there a new flu vaccine every year?

Question

Dr. Ann Woolley, MD · Answer

So, why is there a new flu vaccine every year? Well, the influenza virus, like most viruses, contains a set of genes that are wrapped in a coat of protein. The way vaccines typically work is that for the flu vaccine, it stimulates the production of antibodies that then attach to the outer structures on this protein coat of the virus. And in doing so, it then disables the virus or prevents it from being able to actually enter into our cells and infect us. And so, given that, the way viruses go and the way the flu virus is, is that it is constantly evolving and when it evolves, it changes those outer proteins. And so, therefore, we need a new vaccine that is able to stimulate antibodies against the current proteins that's in the outer coat of the virus. As a result, we know that we have to really do a close surveillance, of which we have internationally, these influenza viral surveillance centers, that are really trying to see if they can anticipate what are the likely strains of the flu virus. That we could they can then use to target the future years vaccine towards. And so, what we do in north America is that we look to see what is happening in the other parts of the world, in Australia, et cetera, to then say can we anticipate that. And so, some years and some seasons we get it very close and accurate, and other seasons we don't. But this is why every year we get a new flu vaccine.

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"Why is there a new flu vaccine every year?"