Some vaccines trigger immunity that lingers on
Smallpox shot protects for decades, researchers find
The smallpox vaccine protects for a lifetime, and so does actual an infection of measles or mumps, according to the first long-term study of immunity to childhood diseases.
And, surprisingly, while a tetanus shot is only supposed to guard against the disease for about 10 years, a team at Oregon Health & Science University found that half the antibodies against the bacterium were still present in the blood 10 years later.
That may explain why the tetanus rate in Sweden is comparable to that in the United States, even though the vaccine is only boosted after 30 years in Sweden, as opposed to every 10 years in the United States.
Mark Slifka of the Oregon Health & Science University and colleagues used blood samples regularly collected from 45 people over a span of up to 26 years to track the degree to which protection against a host of diseases waned over time.
After the September 11 attacks and the subsequent concerns about bioterrorism, the U.S. Centers for Disease Control and Prevention worried that even people who were vaccinated against smallpox before routine immunization stopped in 1972 might not have protection any more.
But Slifka’s team found that it takes 92 years for half the protective antibodies against smallpox to disappear.
Slifka said previous estimates of vaccine effectiveness have usually been based on studying people for just a few years.
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November 13th, 2007 at 6:40 am
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