Well before the September 11 terror attacks, U.S. government officials worried about Saddam Hussein, Muammar Gaddafi and other despots creating and stockpiling biological weapons – and supplying terrorist groups with the means to wipe out entire cities with smallpox infection, for instance.

Because no one had ever followed the health status of people who had acquired immunity to a variety of contagious diseases either through inoculation or infection over time, the U.S. Centers for Disease Control and Prevention could not be certain that people who got a smallpox shot before routine immunization stopped in 1972 were still protected against the virus.

A new study published in the New England Journal of Medicine gives officials at the CDC – and the Department of Homeland Security – one less thing to worry about: The smallpox vaccine confers lifetime immunity.

A team of researchers led by Mark Slifka of the Oregon Health & Science University collected blood samples from 45 people on an ongoing basis for up to 26 years to track the degree to which protection against infectious diseases diminished over time. In the case of smallpox, it takes 92 years for half the protective antibodies against smallpox to disappear from the body.

Cautioning that “[i]t is unknown whether vaccine-induced immunity is as long-lived as that induced by natural infection,” Slifka and his colleagues found that whether immunity is acquired by vaccinations and booster shots, or by multiple exposures to infectious disease, the body keeps producing antibodies for a long, long time. Antibody half-life (the point at which immune response declines 50 percent) is 11 years for tetanus; 19 years for diphtheria; 50 years for chickenpox; and more than 200 years for measles and mumps.

While this study suggests that some booster shots may be unnecessary, because the American healthcare system has emphazied childhood vaccination – often free or at low cost, with or without health insurance coverage – for decades, our bodies can fight off several biologic agents that might have been used to sow terror in our major cities. Are you paying attention, Michael Moore (second item)?

Note: The Stiletto writes about politics and other stuff at The Stiletto Blog.

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