With all U.S. adults now eligible for the COVID-19 vaccine, the paramount question remains: Can or should vaccinations be required, and with what kind of proof? 

With support split sharply along party lines, a narrow majority of Americans favor vaccine passports while six states have prohibited their use.

Some businesses have expressed the desire to mandate vaccination, and over 70% of current or recent CEOs of major companies said they were open to requiring them. 

But recent polling shows only 6% of companies plan to. Many— like Target and Amtrak— are incentivizing it instead while others are offering employees vaccines at the workplace.

In contrast, a growing number of U.S. universities are requiring students to get fully vaccinated against COVID-19 before returning to campus in the fall. The requirement is not dissimilar to other vaccinations required of college students, but the COVID-19 vaccines’ emergency use status could create a legal gray area.

College students are not the only ones likely to face an inoculation ultimatum. A group of lawmakers have called on President Biden to mandate COVID-19 vaccinations for all eligible military personnel. In a December survey, nearly half of active-duty troops indicated they would decline to get vaccinated along with 54% of military spouses.