"The R0 values have important implications for disease control. R0 magnitude indicates the level of mitigation efforts needed to bring an epidemic under control. Mitigation reduces the effective transmission coefficient, now called Re. Re needs to be reduced to less than 1 to ensure cessation of an epidemic, which can be done by rapid case identification, quarantine measures, and physical distancing to prevent secondary transmissions. For childhood diseases such as measles, the cessation of epidemic spread was achieved with an effective vaccine. However, a vaccine has never been a major tool for control of pandemics because they either occurred before the era of modern vaccines or, as in 2009, the vaccine became available only after the first waves had already occurred."