Volume 10, Number 5—May 2004
Research
Ring Vaccination and Smallpox Control
Mirjam Kretzschmar*
, Susan van den Hof*, Jacco Wallinga*, and Jan van Wijngaarden†
, Susan van den Hof*, Jacco Wallinga*, and Jan van Wijngaarden†Table
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 |
| Contacts | ||
| 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) |
| Intervention | ||
| 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) |
