Less Smallpox Vaccine May Be More

Weakened strains may be safer and just as effective

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MONDAY, July 14, 2003 (HealthDayNews) -- Weakened versions of the smallpox vaccine virus may offer the same amount of protection as the current vaccine while reducing the risk of dangerous side effects.

That news comes from a study in this week's issue of the Proceedings of the National Academy of Sciences.

The current vaccine uses the vaccinia virus, a non-lethal relation of the smallpox virus. When injected into a human, the vaccinia virus reproduces and stimulates the body's immune defenses. But the vaccinia virus can cause severe side effects in people who have weakened immune systems that can't keep the virus under control.

People at risk include those with HIV and people undergoing chemotherapy treatment.

In this study, researchers at the U.S. National Cancer Institute used mice to test the effectiveness of weakened versions of the vaccinia virus. They found the weakened versions were able to resist infection and activate the immune system in a manner comparable to the current vaccine.

More information

Here's where you can learn more about smallpox.

SOURCE: Proceedings of the National Academy of Sciences, news release, July 14, 2003

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