Figure 4

Effects of vaccination coverage and contact rates in all places on the control of measles epidemics. We used a scale parameter ranging from 0 to 1 to scale contact rates in school, daycare, workplace, household and neighborhood. For each combination of vaccination coverage V and the scale of all contact rates, the main outcomes were obtained by running the simulation for each of three scenarios: (A) without contact investigations, (B) with contact investigations and less intervention delays for contacts of the index case, and (C) with contact investigations and more intervention delays for contacts of the index case. For scenarios A, B, and C, red cells show the combinations with uncontrolled outbreaks and blue cells represent the simulated outbreak sizes of the combinations without uncontrolled outbreaks. The values of simulated uncontrolled outbreak probabilities are shown with blue numbers in red cells; the values of simulated outbreak sizes are shown with red numbers in blue cells. The frontiers between adjacent combinations with and without uncontrolled outbreaks are shown by the black lines. These simulations suggest: (1) contact investigations play an important role in preventing uncontrolled measles outbreaks and reducing the total outbreak size; (2) without contact investigations but with the lowest scale of contact rates in all places, even an 80% vaccination coverage may prevent uncontrolled measles outbreaks; (3) with contact investigations, reducing the contact rates in all settings may lower the vaccination coverage required to prevent uncontrolled measles outbreaks; (4) with contact investigations and the highest vaccination coverage level, uncontrolled measles outbreaks may be prevented even with very high contact rates in all settings; (5) less intervention delay for contacts of the index case may help contact investigations reduce the number of measles cases.