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Volume 10, Number 5—May 2004


Ring Vaccination and Smallpox Control

Mirjam Kretzschmar*Comments to Author , Susan van den Hof*, Jacco Wallinga*, and Jan van Wijngaarden†
Author affiliations: *National Institute of Public Health and the Environment (RIVM), Bilthoven, the Netherlands; †Inspectorate of Health Care, the Hague, the Netherlands

Main Article


The baseline parameter values

Model parameter Notation Baseline value
Course of the infection
Maximum duration latent period DE 15 d
Probability of transition to infectious state on day τ of the latent period γτ , τ=1,...,DE 0.0 for τ = 1,...,12
0.3 for τ = 13
0.6 for τ = 14
1.0 for τ = 15
Duration infectious period DI 14 days
Case-fatality rate f 0.3
Transmission probability per contact pτ 
with a1 = 0.27, a2 = 0.5
Ratio of infectiousness of casual contact and close contact ring g 0.2
Mean number of contacts in close contact ring (Poisson distribution) μτ(1) 2
Mean number of contacts in the casual contact ring (negative binomial distribution) μτ(2) 14.9 (sd 8.4)
NegBin(4, 0.212)
Probability of diagnosis δτ 
with bi = 0.5, b2 = 0
(b2=6 for first index case)
Time needed to trace contact r(i) 1 day for i = 1,
3 days for i = 2
(3 days for both rings for first index case)
Time window during which vaccination is effective w 4 days
Vaccination coverage c(i) 0.95 for i = 1,
0.5 for i = 2
(0.5 for both rings for first index case)

Main Article