According to a new study as reported in Medical News Today, (http://www.medicalnewstoday.com/articles/131290.php) the smallpox vaccine may last longer than we thought. Smallpox vaccine was thought to have little or no protective benefit after twenty or thirty years. According to this study, people vaccinated over 40 years ago have antibodies and may not even need a booster. You may recall that several trials of smallpox vaccination were stopped after adverse effects and deaths.
Keeping in mind that the last case of smallpox occurred in the late 1970's and routine vaccination stopped around the same time; anti-terrorism experts have been concerned that we humans lack any ability to protect ourselves and that vaccine stockpiles will not be adequate. Although this is only one study...it is still good news.