Flu vaccine may lead to another strain

(NBC) - A new study raises the question could the seasonal flu vaccine have increased the risk for getting H1N1?

Researchers looked at whether seasonal flu vaccines reduced a person's ability to fight swine flu. They found those who got a regular flu shot were 1.5 times more likely to catch H1N1.

Experts are quick to note these studies do not show a true cause-and effect relationship, and they need more research.

Copyright 2010 NBC. All rights reserved.