http://articles.mercola.com/sites/articles/archive/2003/08/30/smallpox-vaccinations.aspxSome 90 percent of people vaccinated for smallpox 25 to 75 years ago are still protected against the disease. Although it was formerly thought that smallpox vaccinations were only effective for three to five years, researchers found that significant immunityenCommunityServer 2008.5 SP1 (Build: 31106.3070)