- The Washington Times - Monday, October 15, 2001

The federal government has commissioned a study to learn if the nation's smallpox vaccine stockpile can be diluted to increase the amount available to fight a potential biological attack using the fatal disease.
The need for protection against the disease, which has been eradicated in its natural form, has become more pressing since the Sept. 11 terrorist attacks. There is no treatment for smallpox once it takes effect. Routine public vaccinations for the disease in the United States ended in 1972 because it no longer was considered a threat.
Some analysts fear that smallpox manufactured by the Soviet Union in the 1980s for biowarfare may have been obtained by rogue nations and could be used in bioterrorist attacks.
Researchers at the University of Maryland School of Medicine in Baltimore and three other institutions will test whether the vaccines can be diluted to one-fifth and one-tenth of their standard dosage and still prove effective. The study is funded by the National Institute of Allergy and Infectious Disease, which is part of the National Institutes of Health.
"It's a very quick way to markedly expand the amount of vaccine that we already have, which on face value in the undiluted form would not be a lot," said Dr. Anthony S. Fauci, head of the NIH infectious disease institute. "It's prudent to be prepared."
The government has 15.4 million doses of smallpox vaccine stockpiled. It has contracted with a vaccine company for 40 million more doses for the public, scheduled for delivery by the end of 2004. However, Health and Human Services Secretary Tommy G. Thompson has said he hopes to have all of the 40 million doses by next summer.
If tests prove the diluted smallpox vaccine to be effective, it could be ready by the end of this year, Dr. Fauci said.
Scientists hope that by diluting existing doses, they can increase the amount of vaccine by fivefold or more without additional manufacturing.
But diluting the vaccine is not meant to be an alternative to the new doses in production, said Dr. Sharon Frey, the lead researcher on the smallpox study at Saint Louis University School of Medicine.
"This is a stopgap measure to make more doses available until that new vaccine is developed," she said.
Over a 21/2-month period beginning next month, researchers at Maryland, Saint Louis, the University of Rochester School of Medicine and Baylor College of Medicine will study 684 adults younger than 32 who have never been vaccinated for smallpox.
The study will test the diluted vaccines to see if they prompt the production of antibodies for smallpox in test subjects.
Scientists also will see if the vaccine, made from the related cowpox virus that is grown on calves, creates a telltale scab at the site of the vaccination, a sign the vaccine is working or "taking."
"We might see a substantial increase in the doses that produce a take," said Maryland researcher Dr. Carol Tacket.
In a pilot study last year by Saint Louis University involving 20 persons, researchers used vaccines diluted by 10 times and by 100 times, Dr. Frey said. The one-tenth doses produced a significant number of takes, while the doses that were 100 times weaker had little effect, Dr. Tacket said.
Anything that would increase the country's limited stockpile is an improvement, said Dr. Neal Halsey, who studies vaccines at the Johns Hopkins School of Public Health in Baltimore.
"I am sure there is nowhere near enough smallpox vaccine to provide it to everyone in the country and even those who would be exposed in a large incident," he said.
Smallpox is a viral disease that causes high fevers, rashes and sores that cover the body. The disease is fatal in about a third of all cases.
While inhaled anthrax is much more lethal, killing roughly 90 percent of all patients, it isn't contagious. Smallpox released in a bioterror attack, however, could spread rapidly throughout a population and infect thousands because it is passed through the air.
Containing an outbreak could be difficult without effective vaccines, Dr. Frey said.
"One outbreak could actually cause an epidemic or a pandemic that would be worldwide," she said.

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