My first investigation as a new Epidemic Intelligence Service (EIS) Officer with the Centers for Disease Control was of a large outbreak of measles, mostly among Hispanic children, many under a year old, and many who became infected when they visited hospital emergency departments for other reasons.
I will never forget how nervous I was. I wanted to do a good job for those children, their families and everyone around them. These infants were too young to be vaccinated, and as a result they were particularly susceptible. So we vaccinated those around them to stop transmission.
By 2000, a decade after my EIS experience, measles transmission in the United States was declared to have been stopped. However, we still have occasional clusters of measles in pockets of unvaccinated children after measles has been brought into the United States from somewhere else in the world.