Table 1.
Model parameter values.
Fig 1.
Ring vaccination with baseline parameters.
A Probability (with 95%CI; exact binomial test) of an uncontained outbreak (more than 300 cases) after introducing one infected case into a fully susceptible population for a range of Re values. The dashed line represents the theoretical value 1 − 1/Re under a homogeneous mixing assumption. B Estimated epidemic prevention potential and 95%CI for a range of Re values. The shaded grey area denotes the most plausible Re values for the 2014–15 West African epidemic. C Mean number of vaccine doses and 95%CIs for containing an outbreak for a range of Re values. D As C but for the number of rings defined. Each estimate is based on 1,000 simulated outbreaks.
Fig 2.
A Estimated epidemic prevention potential (points) and 95%CI (vertical lines) as a function of Re and by varying the vaccine coverage. Baseline coverage: 65% [4]. The shaded grey area represents the range of most plausible values of Re for the 2014–15 epidemic in West Africa. B As in A but by varying the eligible population. Symbols: C indicates contacts of index cases; CC indicates contacts of contacts; S indicates geographical rings (ring radius: 2 km). Baseline value: C&CC [4]. C As in A but by varying the parameter regulating human mobility. Spatial transmission is proportional to a power law kernel 1/(1 + db) where d is the geographical distance and b regulates the decrease of transmission with distance. Baseline value: b = 2.25, resulting in an average distance of 7.7 km [23]. Other scenarios assume different values of b, corresponding to an average distance ranging from 1.5 to 25 km. In these scenarios, probabilities of outbreaks in the absence of interventions were recomputed for each value of the parameter b. D As in A but by varying the time from symptoms onset to hospitalisation. Baseline value: 4 days [9]. Each estimate is based on 1,000 simulated outbreaks.
Fig 3.
A Estimated epidemic prevention potential and 95%CI for a range of Re values using three ring-defining strategies: contacts and contacts of contacts (C&CC) of index cases; C&CC with a spatial ring of radius 2km around index cases (C&CC+S); C&CC+S (2km) plus “improved health systems”, which includes reducing time to isolation of cases (2–3 days from onset to hospitalisation), increasing ring vaccination coverage to 90% of eligible individuals, and reducing public access to infected areas. The shaded grey area denotes the most plausible Re values for the 2014–15 epidemic in West Africa. B As A but considering mass vaccination (coverage 25% and 50%) and a spatial ring (S) of 20km around index cases. Each estimate is based on 1,000 simulated outbreaks.