In most cases, whether they have decided to vaccinate now, later or never, doctors say the parents they counsel have agreed with each other. But when they do not, the battle is part of a new pandemic front in divorce custody battles, one that is poised to expand with the imminent approval of vaccines for children under 5. Last month, Moderna announced plans to seek emergency authorization of their coronavirus vaccine for babies and toddlers after seeing promising results in a clinical study.

Ms. Grote, who wants to vaccinate her children, while her ex-spouse does not, has been divorced since 2019. She and her ex share custody of their daughter and 11-year-old son. As a nurse in an intensive care unit, Ms. Grote has cared for many critically ill Covid-19 patients, but her children remain unvaccinated, a status, she said, that is a result of how her custody proceedings continue to unfold in family court.

“I’m a single mom. I don’t have a ton of money,” she said. “But the money I’ve spent battling this, I could have taken my kids to Disney World, twice.”