The ruling by an arbitration panel means no city workers can be placed on leave for defying the mandate until further notice.
The stay comes one day before the enforcement was set to begin.
It was not immediately known how long the delay would last. The city said it expects the panel to meet in the upcoming days to "determine final consequences for any employee that remains non-compliant."
The arbitration panel involves employees represented by the Fraternal Order of Police, but the delay applies to all represented city employees due to the contracts negotiated with other labor unions, the mayor's office said.
"This stay was issued in light of the significant progress represented in the current figures provided by the Philadelphia Police Department and because parties are still in the process of compiling data regarding vaccinated and unvaccinated officers," a statement from the mayor's office reads.
Philadelphia's vaccine mandate went into effect Friday, Feb. 11. It required city workers to provide proof of having at least the first dose of the vaccine or submit a valid exemption.
All other requirements regarding masking and testing remain in place, the mayor's office said.
The firefighter's union sued the city over the vaccine mandate earlier this month. IAFF Local 22 said the mandate would lead to the suspension of 30% of its members, exacerbating a staffing shortage and therefore risk public safety.
Here are the vaccination rates by department as of February 22:
- Mayor's Office & associated small offices: 91% to 100% vaccinated
- Commerce: 81% to 90% vaccinated
- Fire: 61% to 70% vaccinated
- Fleet Management: 71% to 80% vaccinated
- Free Library of Philadelphia: 91% to 100% vaccinated
- Human Services: 91% to 100% vaccinated
- Innovation and Technology: 91% to 100% vaccinated
- Law: 91% to 100% vaccinated
- Licenses & Inspections: 91% to 100% vaccinated
- Managing Director's Office: 91% to 100% vaccinated
- Parks & Recreation: 91% to 100% vaccinated
- Police: 71% to 80% vaccinated
- Prisons: 81% to 90% vaccinated
- Public Health: 91% to 100% vaccinated
- Revenue: 91% to 100% vaccinated
- Streets: 81% to 90% vaccinated
- Water: 81% to 90% vaccinated