how do scientists make flu vacines if they change all the time?@triona

Question: how do scientists make flu vacines if they change all the time?@triona
- Keywords:
  flu,
  medicine,
  vacine
Asked by unicorn girl to Triona on 17 Nov 2014.
- Tríona O'Connell answered on 17 Nov 2014:
  
  Scientists make an “educated guess” and use statistics to see what the most common types were in previous years. They also keep an eye on what’s happening in the southern hemisphere as they get to have winter while we enjoy summer.
  The vaccine is against three types of flu, (2 A and 1B, or the other way round, I haven’t had coffee yet) and covers the most likely types of flu that are coming up. It doesn’t always catch all types that occur in a winter, but it does a good enough job most of the time

Question: how do scientists make flu vacines if they change all the time?@triona