In the computationally generated networks, CBF outperformed the acquaintance method in large areas of the parameter space ( Figure 4d ). It may seem unintuitive at first that the acquaintance method outperforms CBF at very high values of modularity, but one should keep in mind that epidemic sizes are very small in those extremely modular networks (see Figure 1a ) because local outbreaks only rarely jump the community borders. If outbreaks are mostly restricted to single communities, then CBF is not the optimal strategy because immunizing community bridges is useless; the acquaintance method may at least find some well connected nodes in each community and will thus perform slightly better in this extreme parameter space.