Posted on 08/28/2002 6:31:53 PM PDT by RCW2001
By Merritt McKinney
NEW YORK (Reuters Health) - In what may come as reassuring news for people who were inoculated against smallpox before widespread vaccination against the virus was halted several decades ago, North Carolina scientists report new evidence that the smallpox vaccine may provide protection longer than previously thought.
The duration of this protection has been a bit of a mystery. The results of some early studies suggested that the smallpox vaccine provides long-lasting protection against fatal disease, but "little direct evidence exists," Drs. Jeffrey A. Frelinger and Mohammed L. Garba, of the University of North Carolina at Chapel Hill, point out in a letter in the August 29th issue of The New England Journal of Medicine ( news - web sites).
In an interview with Reuters Health, Frelinger said that when smallpox vaccination was routine in the US, the Centers for Disease Control and Prevention ( news - web sites) recommended revaccination every 7 to 10 years. Implied in this advice, according to Frelinger, was that smallpox immunity "had mostly waned" after several years.
But in a group of 13 lab workers who had been vaccinated against smallpox, Frelinger and Garba detected significant immunity even in people who had been vaccinated more than 35 years ago.
The results suggest that immunity against smallpox is "not seriously gone" 35 or more years later, according to Frelinger.
The researchers evaluated how well immune system cells called CD8 T cells responded when participants were exposed to vaccinia, a virus related to the smallpox virus that is used in vaccines to trigger immunity to smallpox.
Not surprisingly, exposure to vaccinia produced a robust CD8 T cell response in people who had been vaccinated in recent years--due to possible exposure to smallpox in the lab. But the response was still considerable in people who had been vaccinated 6 to 35 years before, according to the report. And even people who had been vaccinated more than 35 years ago still had a considerable immune response.
In recently vaccinated people, about 6.5% of CD8 T cells were activated in response to vaccinia, compared with 4% in people vaccinated 35 or more years before. This level of response would still be expected to provide substantial immunity, Frelinger said.
Based on the results, the North Carolina researcher said that people who were vaccinated in the past should feel "pretty confident" that they still harbor some protection against smallpox.
"I told my father, age 81, he should be OK," Frelinger said.
In the US, the smallpox vaccine was required for school entry prior to 1972, and about 60% of the US population has been vaccinated. The smallpox vaccine was often given in the arm, causing a tell-tale scar to develop. But the absence of such a scar on the arm does not necessarily mean that a person was not vaccinated. Frelinger said that infant vaccinations were often given in the thigh. He noted that a vaccination scar on the leg may be difficult to see, since it is more likely to be obscured by hair.
The eradication of smallpox was officially declared in 1980, and according to the World Health Organization ( news - web sites), national vaccination programs had stopped in all countries by the early 1980s.
The initial signs of smallpox infection include headache, vomiting and fever. Then pus-filled lesions form on the head and face, and may also appear on other parts of the body.
There is no treatment for the disease, which is fatal 20% to 40% of the time in unvaccinated people. However, if an individual has been exposed to the virus and is vaccinated within the next 4 days, it can reduce symptoms or prevent the disease.
Officially, smallpox exists in only two laboratories--one in the US and the other in Russia. However, there are some concerns that other governments or terrorist groups may have samples of the deadly virus.
SOURCE: The New England Journal of Medicine 2002;347:689-690.
Yes, you're protected. Doff the tinfoil hats, for crying out loud, put ice on it (who said that?...I can't remember) and move on. Knock off the hysteria.
Makes me wonder if this is disinformation to calm the masses.
MKM
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