According to the center for disease control (cdc), "measles is highly contagious and can be spread to others from four days before to four days after the rash appears. measles is so contagious that if one person has it, 90% of the people close to that person who are not immune will also become infected with the measles virus." if an individual has a contact rate of approximately 2 individuals per day, what percentage of the population needs to be vaccinated to prevent outbreaks of the disease?