RENO, Nev. (AP) — Nineteen unvaccinated students were forced to temporarily unenroll from a Reno high school to avoid exposure during an outbreak of whooping cough.

Unenrolling during the disease’s 21-day incubation period allows the Damonte Ranch High School students to avoid being classified as chronically absent.

The 19 affected students claimed a religious exemption from the vaccine for whooping cough. The Washoe County Health Department says they should avoid going to school until 21 days after the last student was diagnosed.

A school district official tells the Reno Gazette Journal that the students will be in touch with their teachers and won’t be held back. She says absences because of a lack of vaccination can’t be excused under federal law.

Three students at the school have been diagnosed with whooping cough.