Another example of combination strategy is reduction of pandemic spread through air travel. Suspension of 99.9% of air travel can only delay individual national epidemics by up to four months, while a combination of local strategies reducing influenza transmission by 40% can delay pandemic spread by up to 10 months [13] . A combination of vaccination and travel restrictions may delay epidemic growth, allowing vaccination of susceptible individuals [14] . With a pandemic starting in July in Asia, the number of United States (US) metropolitan cases was 102.4 million -0.1% daily vaccination alone reduced this to 73.0 million, and vaccination together with travel restriction reduced this to 56.9 million [14] .