Some fans attending Sunday's Indianapolis 500 can get measles vaccines at the track's infield medical center.

IndyCar medical director Geoffrey Billows said Thursday a "very limited supply" of vaccines will be available at the medical building near the Indianapolis Motor Speedway museum. He says most insurance companies will cover the cost.

Billows encourages concerned fans to get vaccinated before coming to a race expected to attract in excess of 275,000.

Measles was once common in the U.S. but gradually became rare after vaccination campaigns that started in the 1960s. The nation is struggling with a high number of cases this year as some families choose not to get vaccinated despite the recommendations of public health experts.

At least 20 confirmed cases of mumps also were reported at Indiana University in Bloomington, about 50 miles southwest of Indianapolis.

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