The measles are back.

An outbreak that began in Clark County, Wash., continues to grow this week, with 51 confirmed cases at press deadline. (That number rose to 54 on Wednesday.) The majority of cases were in children under age 10 who had not received the measles-mumps-rubella vaccine.

The outbreak has been fueled by low vaccination rates, as myths about immunizations continue to flummox public health officials. That's a problem in Oregon, too, where one Multnomah County school has a measles vaccination rate of 30 percent.

Oregon requires vaccinations to attend elementary school. But parents can file for medical or nonmedical exemptions to the immunization requirements.

Oregon had the nation's highest kindergarten nonmedical exemption rate in 2013, before the state passed a law requiring parents seeking nonmedical exemptions to review information about the benefits and risks of vaccines.

The exemption rate fell initially but has since risen to an all-time high. In 2018, the percentage of Oregon students with nonmedical exemptions for one or more vaccines reached 7.5 percent.

Here are the schools with the lowest immunization rates in the county.