Assessment of Future Scientific Needs for Live Variola Virus (1999) / Chapter Skim
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7 Development of Vaccines
7 Development of Vaccines
Pages 53-58
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From page 53... ...
The testing of new lots of vaccinia vaccine made using standard methods, or of well-characterized strains of vaccinia grown in tissue culture cells, would not require live variola virus. Although not of overriding concern, retention of live variola virus stocks would, however, permit corroborating assessments of the probable efficacy of new tissue culture vaccines, using laboratory assays to measure immune inhibition of variola replication or testing 53
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From page 54... ...
CURRENT STATUS OF VACCIPIIA VACCINE PREPARATIONS The commercial smallpox vaccine currently approved for use in the United States is a lyophilized preparation of live vaccinia virus prepared from calf lymph. The vaccine is made by inoculating animals with seed virus derived from the New York City Board of Health (NYCBH)
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From page 55... ...
During the history of smallpox vaccination, many different vaccinia isolates and several different animal hosts were used to manufacture vaccine. These diverse vaccines were effective against epidemiologically distinct variola viruses responsible for smallpox outbreaks that were separated by distance as well as time.
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From page 56... ...
These measures of equivalence between vaccines derived from tissue culture and traditional vaccines made in animals would not, however, constitute definitive proof of protective efficacy, which would have to be defined by field testing under conditions of natural exposure. No specific immunologic correlates of protection for vaccinia vaccines were defined during the smallpox era.
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From page 57... ...
The efficacy of any vaccine that was substantially changed in design could not be established by direct comparison with traditional vaccinia vaccines without more complete understanding of protection against variola immunopathogenesis. Confidence in the efficacy of different preparations of live vaccinia vaccines is based on the fact that these vaccines contain the complete virus, and the virus causes a limited infection in the vaccinated person.
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From page 58... ...
Nevertheless, confirmatory assessment of the induction of functional protective immunity would require testing using variola virus, and the margin of confidence in the probable efficacy of such vaccines would be enhanced by studies of challenge by variola virus in animal models yet to be developed. Despite the major obstacles involved, the design of novel vaccines is scientifically feasible, and may constitute a rationale for preserving variola stocks for future use in such an endeavor.
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