Six employees of the Los Angeles Police Department, including a lieutenant, a detective, two officers, and two non-sworn, have filed a lawsuit over a vaccine mandate.

The lawsuit filed in U.S. District Court on Saturday is an effort to overturn the city’s COVID-19 vaccine mandate, KTLA reports.

The suit claims there’s no evidence that natural-acquired immunity isn’t as effective as the jab, the Daily News reports.

“The city does not and cannot point to any evidence that vaccinated individuals have longer lasting or more complete immunity than those who have recovered from COVID,” according to the complaint filed against the city of Los Angeles, its police chief, mayor and administrative officer.

The Los Angeles City Council last month approved an ordinance requiring city employees to be fully vaccinated against COVID-19 by early October, unless they are granted an exemption for medical or religious reasons. Under the mandate, employees would be required to show proof of COVID-19 vaccination or a weekly negative COVID-19 test.

Among the plaintiff group are officers who have “experienced and recovered from COVID-19,” the suit states.

“Studies indicate that these plaintiffs’ natural antibodies and immunity are greater than their vaccinated peers,” the plaintiffs allege.