When people debate partisan issues, Dr. Callaghan said, each side will marshal reasons it is right. “We have a very clear evidence base as to why we need Americans to be vaccinated against Covid-19,” he said. “Whereas with politics, there are two sides and both sides can be heard. But the big difference is that your choice to vaccinate has a huge impact not on only on yourself, but on society as a whole.”

Christine Natalie, 35, of Bennington County, Vt., says it is still too risky for her to join a large Thanksgiving gathering because she has undergone immunomodulation therapy, which would make her more vulnerable if she contracted the virus. Instead, she’ll go to a smaller family celebration where all adults will be vaccinated. Children too young for a vaccine will also attend; the presence of an unvaccinated adult could put them at risk.

“My relatives are more concerned of spreading it to me,” Ms. Natalie said. “I feel differently toward people who haven’t taken the steps to protect others. It shows a lot about their character.”

Billie Jean Van Knight, 43, who has rheumatoid arthritis, doesn’t allow unvaccinated people in her home in St. Paul, Minn., and minimizes her trips outside. But now that she has her booster shot, she feels more freedom. She’ll spend the holiday at the home of her husband’s aunt and uncle, where everyone will have been vaccinated.

“I wish people would just be kinder to each other and think about each other a little more,” she said. “It’s not about your freedoms. It’s about other people’s as well.”

If someone wants to start a Thanksgiving discussion about the importance of getting vaccinated, it’s important to remember that they won’t change someone’s mind during one conversation, said Melody Butler, 35, a nurse from Lindenhurst, N.Y., and the executive director of Nurses Who Vaccinate. People should be prepared to make themselves available to answer questions or continue talking.