Science Buddies: "Ask an Expert"

how does the virus change its surface proteins to get past the vaccine?

You want to post this in the Life Science Forum where there are probably some biologists and you will get some better answers.

All Vaccines that I know of work by teaching the body how to recoginze a pathogen so that it can mobilize the immune system to fight it. The vaccines are typically dead or extremely weak strains of the pathogen that a normal healthy individual can muster an immune system response to and quickly defeat the vaccine's pathogen.

There are a huge number of variations of Influenza viruses that biologists group into different main base strains and the surface protiens are a major characterization factor.

I personally don't know if a virus is capable of significantly altering its surface protiens as that would cause it to belong to a whole different strain. You are going to have to do some serious research into that area if you can't get some help from the Life Science experts.

Flu vaccines take time to produce so it is a major guessing game as to what the most common strain will be each year. Sometimes the guess is way off and the vaccine is not effective against the prevalent strains of flu in some seasons, other times the guess is right on and the vaccine is very effective against the prevalent strains in the season.