Nearly 5,000 parents in Multnomah County were sent exclusion orders by health officials today, warning that if they don't vaccinate their kids before Feb. 20, those children will not be allowed to attend school.

Oregon state law dictates that children in preschool, childcare centers and elementary schools must be vaccinated or be granted an exemption for non medical or medical reasons.

As the Feb. 20 school exclusion deadline approaches, a regional measles outbreak has led to 54 confirmed cases.

Three Multnomah County youths recently contracted measles, The Oregonian reported, bringing the number of Oregon cases to four while Vancouver-area cases are at 50.

"Unfortunately this is a reminder of how quickly infections can spread when people are not vaccinated, and that's especially true in places like classrooms where kids spend a lot of time together," Jennifer Vines, a Multnomah County deputy health officer, said in a statement. "I strongly encourage parents to learn more about measles and the very effective vaccine that can protect their kids."

Health officials say parents who receive an exclusion order should take it and their children to a primary care physician to get necessary immunizations.

For families who are under-insured or do not have health insurance, student health centers and community clinics provide low- or no-cost vaccines.

Multnomah County also plans to host three pop-up immunization clinics for kids to get vaccinated before the Feb. 20 deadline.

Those clinics will take place Feb. 16, 10 am-2 pm at David Douglas High School and Feb. 20, 9 am-3 pm at the East County Health Center.

Update: A clinic scheduled for Feb. 9, 10 am-2 pm at Reynolds High School has been cancelled due to weather.