Employees must tell their employer if they are requesting an exception to a COVID-19 vaccination requirement because of a conflict between that requirement and their sincerely held religious beliefs, practices, or observances.  Under Title VII, this is called a request for a “religious accommodation” or a “reasonable accommodation.”
An employer should proceed on the assumption that a request for religious accommodation is based on sincerely held religious beliefs, practices, or observances.  However, if an employer has an objective basis for questioning either the religious nature or the sincerity of a particular belief, the employer would be justified in making a limited factual inquiry and seeking additional supporting information.  An employee who fails to cooperate with an employer’s reasonable requests for verification of the sincerity or religious nature of a professed belief, practice, or observance risks losing any subsequent claim that the employer improperly denied an accommodation. See the EEOC website for more information.