SAN DIEGO (AP) — A “rock star” doctor who tested tens of thousands of people for COVID-19 in the pandemic’s early months in a badly-stricken California desert community has pleaded guilty to misbranding cosmetic drugs, authorities said Thursday.

Dr. Tien Tan Vo acknowledged in a plea agreement that none of the injectable botlinium toxin, or lip fillers, used by his Imperial Valley clinics from November 2016 to October 2020 were approved by the U.S. Food and Drug Administration, federal prosecutors said.

Vo, who endeared himself to patients for his boundless energy to contain the virus’ spread, admitted purchasing most of the cosmetic drugs from the operator of a “med spa” in Mexicali, Mexico, who smuggled them into the United States without declaring them.

Vo said he received $100,767 for services performed with unapproved drugs and devices.

As part of his plea agreement, the 47-year-old doctor agreed to return the payments and pay a fine of $201,534. He also agreed to pay restitution to victims.

No one answered the phone at Vo’s offices Thursday night.

Motorists lined up for hours at Vo’s clinics in 2020 to get tested for COVID-19 in California’s often-forgotten Imperial County. At one point, the farming region along the Mexican border had the state’s highest infection rate and its two hospitals were overwhelmed. The county is largely Latino and low income,

Alex Cardenas, a former mayor of El Centro, called Vo “a rock star” at the time. The doctor’s two clinics did more than 27,000 tests during the pandemic’s first five months, with a positive rate between 25% and 30%.

Vo, who emigrated from Vietnam as a teenager, often delivered meals and checked on patients at home during the pandemic.

“They really need a doctor here,” he said in 2020. “They’re not very hard to please. They chat with me. They text me every day.”

Vo is scheduled to be sentenced Nov. 16 for receipt of misbranded drugs and being an accessory to an accomplice who smuggled the unapproved drugs from Mexico. Each charge carries a maximum penalty of one year in prison.

“All members of our community should be able to trust that their doctor is acting in their best interest,” said Andrew Haden, acting U.S. attorney for the Southern District of California. “Through this prosecution, we are protecting patients from unapproved and potentially unsafe drugs and will always seek to thwart those who would exploit patients for financial gain.”