Answer: both can have a shelf life!
Yesterday, I had a conversation that reminded me that not everyone realizes this. While some immunizations need only be administered once or as an initial series, it's good to remember immunity provided by some vaccines can wane over time.
The CDC is a great resource if you are curious about your own immunization status. For example, this page offers a revaccination schedule: http://wwwnc.cdc.gov/travel/yellowbook/2012/chapter-2-the-pre-travel-consultation/general-recommendations-for-vaccination-and-immunoprophylaxis.htm.
I hope this information is helpful!
Jennifer Wackerle
Senior Documentation Specialist / Team Leader
Clinical One
