here in Philly with respect to unions opposing vaccination mandates - particularly one local of UNITE HERE (Local 634 for the Cafeteria Workers and School Aides in the school system), many who belong to the very demographics most impacted by covid infections and death. 
One of the main complaints that unions like this and USPS are promoting is that these mandates are "a change in working conditions" and they want to be able to bargain/negotiate it as a change in their contract. Other city worker unions had welcomed the mandates and sold it to their members.
So what the city was able to do was negotiate the change into the Cafeteria workers contract so that they won't be "fired" if they aren't vaccinated but will have to mask and submit to 2X a week testing. They were currently testing once a week as part of the initial masking mandate to open schools in-person. This was announced here yesterday (thus no lawsuit, etc).
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