Even families with multiple health workers at the front of the vaccination line are not yet ready to mingle. Jeanel and Mike Little, nurse practitioners at UVA Health, will both be fully vaccinated by the end of January. But the timeline is far murkier for their 7-month-old daughter, Ruby. Children have been largely absent from vaccine trials, and the virus appears to affect the very young in unusual, and understudied, ways.

“She has been the biggest variable for us,” Mr. Little said. He and Ms. Little will continue to be vigilant about their own hygiene, knowing that they might still be able to transmit the virus, he said. Ruby started day care only in December and has yet to establish regular, in-person contact with any of her grandparents. But for everyone’s sake, that will remain the case for now.

“Our families have not really met our baby,” Ms. Little said. “We won’t loosen those restrictions in the near future; we still need to isolate her as much as possible.”