Preventing second-generation infections in a smallpox bioterror attack.

This article presents a new probabilistic model for the prevention of second-generation infections by different vaccination strategies in the event of a smallpox bioterror attack. The main results are independent of the reproductive number R0 (the number of secondary infections transmitted per index infected individual) and population mixing patterns. General expressions are derived for the fraction of second-generation infections that can be prevented through vaccination, whereas specific results are obtained for traced and mass vaccination, respectively. Expressions for total outbreak size in controlled epidemics are also presented. The analysis highlights the importance of vaccination logistics in addition to beliefs and assumptions regarding smallpox epidemiology in evaluating alternative responses to a smallpox bioterror attack.