CHICAGO (AP) — An arbitrator has upheld the city of Chicago’s COVID-19 vaccine requirement for police. Mayor Lori Lightfoot said Wednesday that she hopes it is a “signal for those members who are not yet vaccinated to get vaccinated.”

The Fraternal Order of Police had vigorously fought the city’s rules which resulted in lawsuits. The ruling says officers must get their first dose of the shot by March 13 and the second dose a month later.

The vast majority of city employees are vaccinated but rates in the Chicago Police Department have lagged behind. The police union didn’t immediately have comment.