There's little doubt that it's legal for workplaces to require employees to be vaccinated, but the question of what's ethical still lingers.

Requiring vaccines is not only ethical, said founding head of New York University's Division of Medical Ethics Art Caplan, but it may be unethical for employers to not put a vaccine mandate in place.

"I keep hearing about the need to pay attention to the rights of the unvaccinated," Caplan said on Greater Boston Wednesday. "Here's what I'd like to do: pay attention to the rights of those who are vulnerable. The elderly, children, people with immune diseases."

"I want the employer to be worrying, first and foremost, how do I keep this workforce safe?" he went on. "How do I keep the relatives, families, partners of those who work here safe? That ought to be the moral priority."

WATCH: Art Caplan on vaccine mandates