Diluted Smallpox Vaccines Effective

[Reasonable Rascal]

‘Diluted smallpox vaccines effective’
CNN.com
March 3, 2002

http://www.cnn.com/2002/HEALTH/03/03/gen.smallpox.vaccine/index.html

“A nearly completed study indicates that diluted forms of smallpox vaccine are effective, meaning the current national vaccine supply of 15 million doses can be diluted to 150 million doses, a leading government scientist said Sunday. ‘I can say with some certainty that it's been a
successful experiment,’ Dr. Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, told CNN…. Scientists conducted two studies to determine whether diluted vaccines would elicit
enough of an immune response to provide protection. In the first experiment, the old vaccine was diluted five times; in the second, the vaccine was diluted 10 times. With the tests nearly complete, Fauci said, ‘Both dilutions are looking good.’”

[Reasonable Rascal]

Smallpox Vaccine Dilution: A Clarification
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The statement regarding possible dilutions of the smallpox vaccine needs to be amended. That the vaccine diluted at 1:10 produced
satisfactory takes approaching 100 percent was fully anticipated, assuming a satisfactory vaccination technique was used.

Note that smallpox vaccine, like other live virus vaccines, contains substantially more virus than the minimum required to obtain a
satisfactory take. This provides a margin to account for loss of titer in shipping and handling and the expected more rapid loss in
titer after reconstitution of the vaccine.

To dilute the vaccine 10-fold would place the vaccine at the edge of a sharp fall in the proportion of takes coincident with a further
decline in vaccine titer. Thus, there is no plan at present to dilute the vaccine beyond the 1:5 level.

--
D.A.Henderson, M.D.,M.P.H.
Director, Office of Public Health Preparedness
Department of Health and Human Services
200 Independence Avenue, SW
Room 636 G
Washington, D.C. 20201