At least 11 states have dozens of patients with measles – a highly contagious and potentially serious disease that had been virtually eliminated as a major threat nearly 20 years ago. It emerges this winter in states where parents can easily avoid requirements to vaccinate children. Washington state has about five dozen cases, mostly involving unvaccinated children under 10, and Gov. Jay Inslee recently declared a state of emergency. Smaller flare-ups are in New York, Illinois, Oregon and Texas.

The federal Centers for Disease Control and Prevention recommends two doses of the measles-mumps-rubella vaccine for all children reaching school age. Vaccination rates of 90 to 95 percent are generally enough to prevent an outbreak, health officials say, but compliance has fallen across the United States. The Pacific Northwest is home to vocal and organized anti-vaccination activists. In Clark County, Wash., some schools have vaccination rates under 40 percent, according to the county Department of Public Health. Its director, Dr. Alan Melnick, says: "There's a lot of misinformation on social media and elsewhere that looks pretty sophisticated. And I think some parents who are otherwise well-meaning are scared."

Though doctors and health officials overwhelmingly say the vaccine is safe and effective, opponents dislike the pharmaceutical industry and government directives affecting their children. Eighteen states make it easy to get an exemption for safety concerns, religious belief or any other objection. Some parents mail in an exemption request simply because it takes less time, effort and money than vaccinating their pupils. In Oregon, parents just have to watch an online education video and submit a certificate of completion. Washington state legislators are considering a proposal that would make it harder for families to opt out of vaccination requirements for personal or philosophical reasons. Anti-vaccine activists protested outside the capitol last week.

Doctor says: "This problem was 100-percent preventable. What we're seeing here does not need to be happening. We should have eradicated measles, not only from the United States but from the world by now." -- Dr. Alan Melnick, public health director for Clark County, Wash.

Previously unvaccinated teen says: "When I started looking into it myself, it became very apparent that there was a lot more evidence in defense of vaccinations, in their favor." – Ethan Lindenberger of Norfolk, Ohio, who got vaccinated after age 18, though his mother objected

Health official says: "All reputable scientific studies have found no relation between measles and autism." -- John Wiesman, Washington state health secretary