Читать книгу Vaccines For Dummies - Sharon Perkins - Страница 14

Most vaccines work well year after year. Some, particularly for influenza, need an update. That’s because some pathogens change their looks. It’s the pathogen equivalent of a wig or a fake moustache that fools our immune systems. What the pathogen looked like last year may not be what it looks like this year, at least to our immune systems.

Pathogens may change their looks by collecting mutations that each make small changes generation after generation. Over time, in a pathogen’s family tree, the great-grandparents may look just a bit different than future generations. There may be different proteins (or sugars) on their surfaces, making them unrecognizable.

The flu does even more to dodge your immune system’s attention. Mutations build up as the flu copies itself again and again. But it does something more. It also mixes and matches the proteins on the outside. It takes a fake moustache and a hat one year, a wig and a mask another year. This means a vaccine that works this year may not work next year. Some types may persist for a few years. Others need to be updated. As we discuss in Chapter 6, a lot of thought goes into the flu vaccine each year, trying to guess six months ahead which fake moustaches and wigs will be en vogue for the flu this year. The vaccine is updated every year in both the Northern and Southern hemispheres in time to vaccinate everyone who wants it in preparation for the wintertime flu season.