Health care company One Medical charged administration fees to some people receiving COVID-19 vaccines in Washington, DC, according to bills reviewed by The Verge. The company runs the COVID-19 vaccination site at DC’s Entertainment and Sports Arena. People vaccinated at this site were also prompted to sign up for a trial account with One Medical to receive the shots.

One Medical told The Verge in a statement that an error in the billing system led to the charges, that impacted patients “are being notified,” and that they should disregard the bill. “We are monitoring daily to ensure that no new invoices are going out,” One Medical said.

There is not supposed to be a charge associated with the COVID-19 vaccine, according to the Centers for Disease Control and Prevention (CDC). Vaccine providers can get reimbursed by insurance companies or federal programs for the cost of administering the vaccine, but the CDC’s “Frequently Asked Questions” page says that they cannot charge patients that administration fee directly. The DC Department of Health did not respond to a request for comment by publication.

Chris Driver, who lives in Northeast DC, says he was charged by One Medical for both doses of the Pfizer vaccine. He provided his insurance information when he signed in for the first shot but was still billed a total of $56.94 — $16.94 for the first dose, and $40 for the second dose. After receiving the bill for the first dose, Driver tweeted at One Medical on March 18th asking why he was charged. The company responded that it would remove the charge. Over two weeks later, the first charge was still listed on his account, and the second dose fee was added.

The charges appear to be inconsistent. Driver’s wife was also vaccinated at the One Medical site, but he says that she did not receive a bill. But another person who got a first dose of the vaccine at the One Medical site was charged $40 by One Medical, according to a bill reviewed by The Verge. That person — who wished to remain anonymous to discuss personal health information — did not give their insurance information when they got the shot.

Health officials around the country are working to improve vaccine equity by removing barriers to sign-ups like complex websites or the perception that there’s a charge associated with the shot. It’s a big problem in Washington, DC, where more affluent areas have far higher vaccination rates than poorer areas and communities of color.

“While I can afford a random $55 medical bill if it came to it, I know that’s not always the case for a whole lot of people in the city,” Driver said in a Twitter direct message. Millions of people say they aren’t going to get vaccinated because they’re worried about costs, according to a US Census survey — even though the vaccines are free. “The federal government is providing the vaccine free of charge to all people living in the United States, regardless of their immigration or health insurance status,” the CDC’s website says.

People getting shots in other states have also been stuck with bills. One Houston, Texas-area clinic charged people $30 for each dose of the vaccine, 13 Investigates found. The Texas Department of State Health Services told 13 Investigates that providers should not be charging people a fee.

One Medical, which was backed by Alphabet’s venture capital group, GV, provides concierge primary care in over a dozen cities (including Washington, DC) for a $199 annual fee. A handful of states gave the company vaccine doses to administer. An NPR investigation in February found that it was giving shots to people who were not eligible in California and Washington state. Those states stopped giving vaccines to One Medical after receiving complaints.

Tech executive Lucy Caldwell tells The Verge she canceled her One Medical membership after a family member was charged for the COVID-19 vaccine at its site in Washington, DC. In an emailed response to her complaint, a representative told her that bills went to patients “by default” if they did not give insurance information. The representative said that charges are removed if the company is notified and that “dozens” of people had that problem.

People vaccinated at the One Medical site were also asked to sign up for a trial membership of its health service. “That pinged as a red flag for me, because I couldn’t believe the city was asking people to sign up for some health care subscription service in order to get the vaccine,” Driver said. “But, I did it because I wanted to get the dang shot.” The free trial sign-up did not ask for billing information, and it said the service would not auto-renew.

One Medical told The Verge that it needed the information in order to create a patient chart for people vaccinated at its site.

Privacy watchdog groups have been worried about private companies using the COVID-19 vaccine administration process to collect personal data on potential customers. Pharmacies like Walgreens require that people create an online account in order to sign up for a vaccine appointment. Consumer rights organizations asked Democratic state attorneys general to investigate how the companies are using that data.

“We don’t want to see folks in their desire to get vaccinated — and frankly, protect themselves and their loved ones — be in any way taken advantage of,” Andrew Crawford, a lawyer at the Center for Democracy and Technology, told Politico.