Photo: CDC
With the start of the new school year around the corner – and as a measles outbreak continues in three Oregon counties – health officials are urging parents and guardians to get their children vaccinated against the highly infectious virus before classes begin.
A total of 25 confirmed cases of measles have been reported in Clackamas, Marion and Multnomah counties, all among unvaccinated individuals. Two people have been hospitalized, and there have been no deaths. Ten of the cases are 9 and younger; 10 cases are ages 10 to 19; and five cases are 20 and older.
Marion County has the most cases with 16, followed by Clackamas County with eight and Multnomah County with one.
Paul Cieslak, M.D., OHA medical director for communicable diseases and immunizations, joined Clackamas County Health Officer Sarah Present, M.D., for a media briefing this morning to give an update on the outbreak.
Cieslak said state and county epidemiologists have seen several waves of measles cases since mid-June, “so now about two months of sustained transmission of measles.” It’s the largest measles outbreak the state has seen since 2019, when Oregon experienced 28 cases that were linked to a much larger outbreak in Clark County, Wash.
“Before 2019, you have to go all the way back to the early 1990s to see case counts this high,” Cieslak said. “The reason is we maintained very high vaccination rates and very high population levels of immunity. Unfortunately, we’ve seen an erosion in the percentage of people who are getting vaccinated against measles.”
Since about 2000, an increasing number of parents have chosen nonmedical exemptions from state school vaccination requirements for their children. Before that year, only about 1% of kindergarteners had vaccination exemptions; since then, the number has risen steadily, and during the 2023-2024 school year, the exemption rate reached 8.8%.
“In Clackamas County, as in other Oregon counties, pockets of unvaccinated people raise risk of infection in communities where they live,” Present said. “That’s why the counties reach out to every case that’s been identified and try to determine exactly where they’ve been while infectious.”
Someone with measles can spread the virus up to four days before the tell-tale rash appears, and their symptoms may be mild during that time. As a result, the counties and OHA have been sharing information about specific locations that cases are known to have visited, so “we can let members of the public know they may have been exposed to measles,” Present said.
She noted that since measles is so contagious, an estimated 95% of a population needs to have received two doses of measles vaccine to be able to protect the most vulnerable members of the community via community or “herd” immunity.
Getting the MMR vaccine can also help families avoid the burden of having to isolate at home for several weeks if they are exposed to measles. According to state law, an unvaccinated person exposed to the virus must be excluded from school or child care during the period when they could become sick, which is usually for 21 days after exposure. And this exclusion can be extended if there are more measles cases.
“It’s really an important time to make sure students and their families are up to date on vaccinations as we go into the new school year,” Present explained.
Learn more about measles at https://www.oregon.gov/oha/PH/DISEASESCONDITIONS/DISEASESAZ/Pages/measles.aspx.