The number of measles cases in Minnesota, all of them in Hennepin County, has grown to nine.
Four of the nine Hennepin County cases are among children too young for vaccination. Four more are among people who were not vaccinated.
Hennepin County public health officials are holding measles vaccination clinics, but so far, they say, attendance is poor.
"We were really trying to target the Somali community in particular and addressed our ads and have not been effective in getting our message out," said Allain Hankey, an epidemiologist with the Hennepin County public health department.
Somali children account for five of the nine measles cases in Minnesota, including the two identified late Monday. Health officials are concerned about lower rates of vaccination in that community.
But Hankey said she's worried about the broader decline in the number of children in Hennepin County with vaccinations.
"The overall vaccination rate at age two is about 85 percent right now," Hankey said. "We ought to be well over 90 percent in our community."
Lynfield, who is also a pediatrician, said some Somalis fear vaccinations are linked to autism, a connection that she said has been debunked.
Other Minnesotans, she said, refuse to have their children vaccinated for other reasons, including exposure to foreign proteins.
"The reality is their children are exposed to lots of foreign substances every day," she said. "The reason we use vaccines is they are a safe way of exposing the child to something that is similar to the infectious agent, so that if the child does get exposed to the infectious agent they now have a stronger response to it."
The nine cases of measles in Minnesota so far this month, Lynfield said, are more than the reported number of cases in the past five years combined.
She said measles was mostly contained in years past because of widespread immunity among state residents.
"Unfortunately this time around it came in a population that did not have a high amount of immunity," Lynfield said. "There was the opportunity for the measles virus to circulate and cause more infections. It is very, very contagious."
Lynfield said people without immunity who are exposed to measles have a 90 percent chance of infection.
Measles, also called rubeola, is rarely fatal, but can cause complications including pneumonia.
Lynfield said she expects the number of cases to rise.
Hennepin County public health officials are scheduling another measles vaccination clinic for Saturday at Children's Hospital in Minneapolis.