turned it down.)

research on this trait.

“In other words, these cultural ideals lead men to avoid important health care in order to act masculine,” she said. “Now that the vaccine is available to everyone, it will be interesting to watch male-female differences in vaccine uptake, because these will more likely reflect social and cultural ideas about gender and health, such as the cultural idea that ‘real men’ don’t need preventive health care.”

At this stage, U.S. health authorities have not released data on nonbinary adults and vaccination.

There may also be political connections. Women are far more likely than men to register as Democrats, and polls demonstrate that Republicans across the country have been far less likely than Democrats to embrace the vaccine.

So who will men listen to? Not their wives and female friends or doctors, it seems. For their recent preprint study, Leah Witus and Erik Larson, professors at Macalester College in Saint Paul, Minn., watched videos with men and women that featured identical information about the vaccine. Among the 1,184 Americans who watched them, most were positively influenced by the male narrator while the female narrator got a far more mixed response.

“The male-narrated version of the video increased vaccination intention in viewers,” said Ms. Witus, “but the female-narrated had mixed associations with vaccine propensity, and in some viewers, those that identified as conservative, actually decreased vaccination intention.”

This may spell victory for Mr. Schillaci as he and his wife subtly joust for influence over their 20-year-old son’s vaccination decision. Mr. Schillaci has been sharing his views with his son, whom his wife is prodding to take a shot.

“I would rather he got the shot, and I hope that he’ll consider it,” said Ms. Elgison.

But Ms. Elgison’s own decision may benefit her son, even if he decides against the vaccine.

As often happens in life, men may find their gaps covered by women. “To the extent most people live and socialize in a mixed-gender setting, the men will benefit from the higher coverage among women,” Ms. Buttenheim said.

Ms. Elgison, however, still has a trump card she hopes might work. “I would like my son to get it so we can all travel together,” she said. “I explained to him that it’s possible that we could protect his dad.”