Health officials in Arizona are pressing federal officials for better cooperation after an outbreak of measles at an immigration detention center was prolonged because some employees were slow to be vaccinated.

The outbreak started in late May in the detention center in Eloy, Ariz., and has grown to 22 cases, currently the largest episode in the country of the disease, which was once eradicated in the United States. The cases include nine employees of the facility, which is overseen by Immigration and Customs Enforcement, a federal agency.

“What was surprising was the failure by the organizations that run the facility to make sure their staff was vaccinated,” said Thomas Schryer, the director of public health for Pinal County, home of the center. “The lingering issue has been the staff passing the illness among each other and going out into the community.”

The facility, 65 miles southeast of Phoenix, holds about 1,250 immigrants from many countries, both men and women, who are awaiting court proceedings or deportation. They include migrants who have come in recent months from three violence-torn countries in Central America. The center is supervised by the federal agency but operated by a private prison company, Corrections Corporation of America, or CCA, which has more than 300 employees.