Wednesday was the deadline for Penn Medicine employees to get vaccinated against COVID-19, and at least 99% have done so, health system officials said during a public question-and-answer session on the pandemic.

Some of the remaining 1% may have been vaccinated but not yet confirmed, while a few unvaccinated employees may quit or else be “terminated for noncompliance,” chief medical officer Patrick J. Brennan said.

The health system announced its mandate in mid-May, the first such move by a large Philadelphia-area employer.

”We’re in the final stages of cleaning up all of our data,” he said.

Brennan’s update came amid answers to a flurry of other questions for the six panelists, all of them pandemic veterans who have grappled with the coronavirus from every angle: its biology, the science behind how the immune system responds to it, and how best to treat infected patients.

Onyeka Nwankwo, chair of infection prevention at Pennsylvania Hospital, fielded a question about the vaccines’ impact on reproductive health, saying that topic is the most frequent one that comes up with patients. The evidence continues to be reassuring, with the latest studies finding that vaccination has no impact on pregnancy or fertility, he said.

Panelists also addressed the hot-button issue of booster shots, saying it was too soon to recommend additional vaccine doses except for those who are immunocompromised — a call for boosters from the Biden administration.

With schools reopening this month, infectious disease specialist Susan E. Coffin counseled parents on how best to protect children too young to be vaccinated. Masks and ventilation remain the key tools, along with urging vaccination for adults who spend time in children’s midst, said Coffin, who treats patients at Children’s Hospital of Philadelphia and is a professor at Penn’s Perelman School of Medicine.

Asked whether a vaccinated person, if infected, can develop the chronic condition known as long COVID, she said the answer was unclear.

But E. John Wherry, director of the Institute for Immunology at the Perelman School, added a reminder. The vaccines are nevertheless the best available weapon against chronic symptoms.

”If you don’t get COVID,” he said, “you’re not going to get long COVID.”