Robocalls may have met their match in the pandemic.

The number of scam calls to phone lines in the United States dropped by half at the start of the pandemic, as lockdowns closed the call centers necessary to robocall enterprises and reduced the number of phone lines with a person on the other end.

Robocalls, auto-dialed calls that usually come with a recorded message that attempt to cheat victims, started coming back after the initial decline. Then Covid-19 walloped India, and calls fell almost 20 percent from March to May as the disease surged and prompted states and cities to institute a new wave of lockdowns.

Alex Quilici, CEO of the voicemail provider and scam-blocking app YouMail, said the lockdowns have had the side effect of preventing people who work at call centers from going into those call centers.

“They couldn’t leave their homes, so they couldn’t do the scams,” Quilici said. “No point of making a robocall if no one’s there when you press 1.”

India, along with Pakistan and the Dominican Republic, are among the main origin points for illegal robocalls involving Social Security, debt collection, and bogus utilities, said Josh Bercu, vice president of policy and advocacy at USTelecom, the association that organizes the industry’s robocall tracing efforts. “Those types of pure fraud almost always are coming from overseas,” Bercu said.