Decades-old smallpox vaccinations may still protect /USA Today

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Decades-old smallpox vaccinations may still protect

 

 

 

 

 

 

http://www.usatoday.com/news/attack/2001/11/08/smallpox-usat.htm

 

 

11/08/2001 - Updated 11:55 AM ET

 

Decades-old smallpox vaccinations may still protect

 

By Rita Rubin, USA TODAY

 

While many Americans worry that bioterrorists will strike with

smallpox before the USA has enough vaccine, studies suggest that people

immunized 50 years ago or more still have some protection. Researchers also say

mass immunization probably wouldn't be necessary because smallpox is not as

contagious as other bugs such as measles or the flu. " It's not going to be the

Armageddon that some would have you believe, " says smallpox expert James LeDuc

of the Centers for Disease Control and Prevention. In some countries, smallpox

was eradicated after less than two-thirds of people were immunized, LeDuc says.

 

 

When it comes to smallpox vaccine, the immune system appears

to have a long memory. " Even if you're over 50 years old and saw the vaccine

when you were a child, the risk of dying from infection is much less than if

you've never seen the vaccine, " LeDuc says.

 

The United States stopped giving smallpox vaccinations in

1972, but the government wants to stockpile doses in case of an attack.

 

LeDuc says the CDC this month will rewrite a section of its

Web site to better explain the issue of residual immunity. Currently, the Web

site states that smallpox vaccine protects for only three to five years.

 

A 1913 report about a 1902-03 outbreak in Liverpool, England,

provides the earliest clues about the vaccine's legs. The study analyzed the

severity of disease in 1,163 people.

 

There were 55 cases among people 50 and older who had been

vaccinated in their childhood. Only four were severe, and only three died, says

Frank Fenner, co-author of Smallpox and Its Eradication and researcher at the

John Curtin School of Medical Research in Canberra, Australia. By comparison,

Fenner says, the disease killed six of the 12 victims 50 and older who had never

been vaccinated.

 

In 1996, scientists from the University of Massachusetts

Medical Center in Worcester reported that immune cells from healthy volunteers

recognized the vaccinia virus — used to immunize against smallpox — as a foe.

Yet up to 50 years had passed since the volunteers' smallpox vaccinations.

 

It's not clear how the immune response seen in the lab would

translate into real life, says study co-author Francis Ennis. While immunity

persists for decades, Ennis says, it most likely does wane over time.

 

 

 

 

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