What is the immune system not efficient at doing (how can it be improved)?

Question: What is the immune system not efficient at doing (how can it be improved)?
- Keywords:
  efficient,
  improve
Asked by Aown to Carmen, Daniel, Laura, Noel, Steph on 17 Mar 2015.
- Noel Carter answered on 17 Mar 2015:
  
  It doesn’t cope well with viruses that change from year to year very well such as flu.
  I am not sure I am clever enough to think what I would change. The problem is it is a very complex system and changing one bit would have unintended consequences for other bits!

Question: What is the immune system not efficient at doing (how can it be improved)?