Employers are allowed to make business decisions only within the boundaries of the law.
Employment in Pennsylvania is "at will," unless you have a contract with your employer, or you are a member of a union with a collective bargaining agreement. If you are a member of a union, contact your union representative. If you believe that you have been terminated inappropriately, you may wish to consult with an attorney familiar with labor and employment law.
You can make a complaint against a business not following required COVID-19 protection measures using the Department of Health's Complaint Form.