In empirical networks, CBF did particularly well on the network with the strongest community structure (Oklahoma), especially in comparison to the similarly effective acquaintance method with n = 2. (Figure 5c ). As immunization strategies should be deployed as fast as possible, the speed at which a certain fraction of the . Assessing the efficacy of targeted immunization strategies based on deterministic and stochastic algorithms in the computationally generated networks. Color code denotes the difference in the average final size S m of disease outbreaks in networks that were immunized before the outbreak using method m. The top panel (a) shows the difference between the degree method and the betweenness centrality method, i.e. S degree 2 S betweenness . A positive difference (colored red to light gray) indicates that the betweenness centrality method resulted in smaller final sizes than the degree method. A negative difference (colored blue to black) indicates that the betweenness centrality method resulted in bigger final sizes than the degree method. If the difference is not bigger than 0.1% of the total population size, then no color is shown (white). Panel (a) shows that the betweenness centrality method is more effective than the degree based method in networks with strong community structure (Q is high). (b) and (c): like (a), but showing S degree 2 S randomwalk (in (b)) and S betweenness 2 S randomwalk (in (c)). Panels (b) and (c) show that the random walk method is the most effective method overall. Panel (d) shows that the community bridge finder (CBF) method generally outperforms the acquaintance method (with n = 1) except when community structure is very strong (see main text). Final epidemic sizes were obtained by running 2000 SIR simulations per network, vaccination coverage and immunization method. doi:10.1371/journal.pcbi.1000736.g004 network can be immunized is an additional important aspect. We measured the speed of the algorithm as the number of nodes that the algorithm had to visit in order to achieve a certain vaccination coverage, and find that the CBF algorithm is faster than the similarly effective acquaintance method with n = 2 at vaccination coverages ,30% (see Figure 6 ).