The U.S. Supreme Court reversed a lower court ruling allowing ballots to be mailed in after Election Day, which likely caused more people to vote in person. Many have wondered whether in-person voting increased the spread of the coronavirus, a question particularly raised for Milwaukee, which had only five polling stations that drew long lines of people.

At least 23 people who voted in person or served as poll workers have tested positive for COVID-19, but many of them reported other potential exposures to the coronavirus, state Department of Health Services spokeswoman Jennifer Miller said Friday.

In the new study, researchers looked at rates of COVID-19 in Wisconsin — and in Dane, Milwaukee and Waukesha counties — for a 10-day period before the election and in the 10 days afterward in which cases would likely arise, comparing the rates to the rest of the country.

The post-election period was April 12-21, or five to 14 days after the election, the time period when health officials say COVID-19 cases typically arise.