Researchers trying to stretch stockpile of smallpox vaccine

BETHESDA, Md. -- Researchers are beginning a large new study to see if they can dilute the nation's small stockpile of smallpox vaccine to make it stretch further in case of a bioterrorist attack.

Fresh batches of vaccine are on order, but experts hope that adding more liquid to the existing supply will be a temporary solution at least until those begin to arrive next summer.

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, and routine vaccinations ceased in the United States in 1972 because it was no longer considered a threat. Most people vaccinated before then have lost their resistance to the virus.

Some experts 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.

The government has 15.4 million doses of smallpox vaccine stockpiled at secret warehouses around the country. Researchers at four institutions will test whether the vaccine can be diluted to one-fifth and one-tenth of their standard dosage and still prevent infection.

"It's a very quick way to markedly expand the amount of vaccine that we already have," said Dr. Anthony S. Fauci, head of the National Institute of Allergy and Infectious Disease, which is funding the experiment. "It's prudent to be prepared."

If it works, Fauci said the diluted vaccine could be ready by the end of this year.

A stopgap measure

However, 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 St. Louis University. "This is a stopgap measure to make more doses available until that new vaccine is developed."

Over a 2 1/2-month period beginning next month, researchers at St. Louis, the University of Maryland, the University of Rochester and Baylor College of Medicine will study 684 adults under the age of 32 who have never been vaccinated for smallpox. They will see if the diluted vaccines trigger production of antibodies and create a telltale scab.