On a day when attention was focused on Pennsylvania’s key role in the U.S. presidential election, the coronavirus marked the occasion with the state’s biggest one-day increase in cases.

State officials reported 2,875 new confirmed cases of COVID-19 on Tuesday, bringing the statewide total to 214,871. The previous one-day record was Oct. 27, when the state Department of Health announced 2,751 new cases.

And if voters spent too long indoors as they waited to cast ballots, infectious-disease experts warned, Election Day could fuel the spread of additional infections. While many polling places were equipped with hand sanitizer for those who touched voting machines and other surfaces, evidence suggests that most COVID-19 cases are spread through the air, meaning good ventilation and masks are important. Though mask-wearing was widely encouraged, voters who refused to wear one would not be turned away, officials had said.

In Philadelphia, the Department of Public Health announced 614 additional confirmed cases of COVID-19 on Tuesday, bringing the cumulative total to 45,582.

In New Jersey, health officials reported 1,832 new cases, still well below the state’s daily totals in April, when the numbers of new cases each day regularly exceeded 3,000.

The numbers of hospitalizations also continue to rise in both states, though hospitals generally remain able to accommodate the increase.

Health officials said 1,352 people were hospitalized with COVID-19 in Pennsylvania, including 301 in intensive care.

The impact of Election Day voting on the resurgence remains to be seen. The pandemic modeling project led by physician David Rubin at Children’s Hospital of Philadelphia surveyed states to ask about practices to ensure safety while voting in person.

“We are happy to report that many states have recognized the importance of pandemic-proofing their voting protocols,” Rubin’s PolicyLab team blogged on Saturday.

New Jersey and Pennsylvania made mail-in voting an option and adopted precautions at polling places, including masking, social distancing, table partitions, hand sanitizer and PPE training for poll workers. The PolicyLab survey found states with big outbreaks, notably Arizona and Wisconsin, had changed their procedures to improve safety. However, Texas, Louisiana, Mississippi, Tennessee, and Indiana did not offer mail-in votes, so 34 million voters had to vote in person — unless they did so with absentee ballots.

While the election’s impact is an unknown, PolicyLab this week looked at rapidly worsening areas throughout Ohio, Michigan, and Pennsylvania and projected that transmission rates will increase over the next four weeks across New Hampshire, Massachusetts, Rhode Island, Connecticut, and New Jersey. “New York City continues to be the stalwart, growing more slowly than the rest,” the team wrote.

On a more promising note, British researchers said immune-system agents called T cells were found in the blood of 100 health-care workers six months after they tested positive for infection with the coronavirus.

The results have not yet undergone peer review, the vetting process that occurs before a study is formally published. And the researchers said it was not yet clear how much these T cells would protect against reinfection.

Nevertheless, they said the findings were an important reminder that in addition to antibodies, which can decline over time, the immune system has multiple layers that may ward off COVID-19.