Start with giving them this letter.
Once given to them, if you are fired, smile at the money they are going to lose in a civil lawsuit to you.
Smart employers will pass this letter to their legal council, and when their council informs them of the multitude of laws they will be violating by forcing the "vaccine", they should quickly back down.
Is there any method for those in "at-will" states or places without contracts, other than probably getting fired for "unrelated reasons" and trying to get unemployment benefits?
Religious exemptions are never going to work imo unless you're very lucky. You also usually have to provide a detailed explanation, which is tricky to craft to be covered under a communist judge's interpretation of civil rights. Church of christian science "admin" has also been taken over by commies so good luck getting support from them.
The only other way would be medical exemption. Best method for that would be to get a new primary care physician, a visit to a new clinic, and "be open with your doctor" about your allergies after writing them down on the intake forms.
I think many parents with dependents will likely just resort to printing out index cards if this continues. Between losing your house/feeding kids and writing some crap down on an index card, I think people would rather have a roof over their heads. Is there any way for an employer to check on the veracity of index cards? Either that or roll over to the JaBbeRiNo