A healthcare worker with a history of measles vaccination still acquired the disease when treating unsuspected cases in the early stages of a large measles outbreak in the Minneapolis area last year, says Julie LeBlanc, MPH, CIC, healthcare epidemiologist at Children’s Minnesota.

The transmission occurred at the beginning of an outbreak that would ultimately result in 75 confirmed measles cases in the community of the Twin Cities. An ED nurse with documented receipt of two doses of the measles, mumps, and rubella (MMR) vaccine was infected after prolonged contact with two cases that were not suspected of having measles.

Another reported hospital-acquired case of measles was the mother of a patient, Leblanc says. Both resulted in mild illness, but added to the chaos as the hospital responded to the outbreak in the community.

“The healthcare worker did not work while symptomatic, and once you are four days past the rash phase you are not contagious anymore,” LeBlanc says. “So once that timeline is met and there are no longer any symptoms, then that person is allowed to come back to work.”

As measles vaccination is not 100% effective, the policy at the hospital is for healthcare workers treating known or suspected cases to wear an N95 respirator regardless of immunization status.

“You wear an N95 if you are medically cleared and have done the fit-testing, or wear a PAPR [powered air purifying respirator],” she says. “Once we knew we had measles, staff really understood their role in identifying any potential suspect case and getting airborne precautions implemented. We had good compliance.”

The hospital policy requires measles immunity on hire. To meet this, the CDC requires new employees to receive two doses of the MMR vaccine or show proof of immunity. Healthcare workers born before 1957 may be presumed to be immune, according to the CDC. However, in the event of an outbreak, the CDC recommends that healthcare workers born before 1957 receive two doses of MMR vaccine.

“In the outbreak, there was really a broad message to staff that they could potentially be exposed with as many cases as we were seeing,” LeBlanc says. “[We said] make sure that you are immune. If you have any question in your mind, work with employee health services to ensure that you meet the policy.”

The outbreak was sparked by unvaccinated children in the area’s large Somali population. There have been past outbreaks associated with the population, some of whom did not vaccinate their children due to antivaccine groups pushing the debunked connection between MMR receipt and autism.

The parents and older children were largely vaccinated, but the younger Somali children were largely unvaccinated, says Patricia Stinchfield, MS, RN, CPNP, infectious disease nurse practitioner and senior director of infection control at the hospital.

“We really realized the impact of the antivaccine groups when we looked at our vaccine records and we saw the oldest kids were vaccinated, the middle kids had one MMR, and the youngest kids had no MMR but every other [childhood vaccine],” she says.

“There are some antivaccine groups in Minnesota. They met with the Somali imams and basically told them to tell their mosque members that MMR causes autism. That myth and the fear took hold.”