Question: How can scientists make a vaccines if viruses are changing?

Hayley Clissold answered on 25 Jun 2015:

Making effective vaccines is a constant challenge!

For example, the influenza vaccine changes every year to keep up with the constantly changing nature of the influenza virus.

Every year, scientists look at which types of influenza viruses are making people sick, how these viruses are spreading, and how well the previous years vaccine worked. All these factors are considered when developing a new influenza vaccine each year!