How often do you need small pox vaccination?

Never: Smallpox is a dead disease. It has been eradicated. Military personnel may be give smallpox vaccine because of the fear that some nation storing the virus may use it as a biologic weapon. Other than that, forget about it.

You don't: The WHO announced World-wide eradication of Smallpox on May 8 1980. Smallpox has no animal reservoirs. So Smallpox would not return naturally. The American public has not received routine smallpox vaccinations since 1972. The government only provides smallpox to several hundred scientists/ medical personnel in research settings.