Well, there are: Are different types of influenza ; the viruses can mutate. The vaccination you receive may or may not be a match to the influenza virus that you are exposed to.
Answered 1/4/2014
4.6k views
A doctor has provided 1 answer
3 doctors weighed in across 2 answers
4 doctors weighed in across 4 answers
3 doctors weighed in across 2 answers
90,000 U.S. doctors in 147 specialties are here to answer your questions or offer you advice, prescriptions, and more.
Ask your question