"Individuals who comply with the advice of health authorities morally condemn the unvaccinated for violating a social contract in the midst of a crisis," two Denmark-based scientists wrote in their paper, published Thursday in Nature.

"Those who refuse vaccines report that they feel discriminated and pressured against their will."

To measure COVID-19 vaccination status-based prejudice, researchers asked some 15,233 people how they feel if a close relatives of theirs are going to marry a vaccinated or unvaccinated person—a question that has long been used in surveys on discrimination along racial, ethnic, or partisan lines.

Specifically, participants were presented with brief descriptions of a series of fictitious individuals and asked to imagine that these are people whom one of their close relatives intends to marry.