Vaccine
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During a mass smallpox immunization campaign, vaccine may be exposed to ambient temperatures for extended periods of time. ⋯ After 2 weeks, viability was greater than 10(7)pfu/ml, the titer suggested by Frey et al. as necessary to ensure successful vaccination in more than 97% of vaccinees. When removed from refrigeration, keeping the vaccine on ice lowers the decline in titer.