Major pharmacy chains aren’t making huge sums of cash by helping to distribute COVID-19 vaccines, but they are reportedly figuring out how to take advantage of the situation in other ways.

Walgreens, CVS and Walmart are all collecting large amounts of customer data when people go to their pharmacies to get COVID-19 shots, according to a Tuesday report from The Wall Street Journal. Emails, phone numbers, medical information and more are reportedly being scooped up by the corporations and being used to perfect targeted marketing and promotional material.

All three pharmacies, along with some other retailers, are enrolled in a federal program that is distributing vaccines directly to the chains’ stores. The policy began in February and was aimed at speeding up the U.S.’s effort in increasing vaccinations for the public.

The pharmacy chains are using customers’ contact information to stay in touch with them throughout the two-dose COVID-19 vaccination process, according to The Wall Street Journal.

“We have their email, we have their text message, and we have the ability to communicate with them regularly,” CVS chief operating officer Jonathan Roberts said to The WSJ. (RELATED: Is Fauci Right? Is America The ‘Worst’ When It Comes To COVID-19?)

At least eight million vaccine recipients at CVS locations had not had a prescription filled through the chain the previous year, meaning the company has brought in millions of potential new customers through its federal partnership. While the companies admitted to using this new customer data for promotional purposes, a CVS spokesman declined to tell The WSJ whether or not medical information learned during vaccination visits would be used.

Anyone seeking a vaccine at Walmart is required to sign up for the superstore’s online patient management program, allowing the company to enroll millions of new customers into its databases. Walgreens has a similar requirement, forcing consumers who want to make a vaccine appointment to sign up on the company’s website.

A spokesperson from Walgreens says vaccine recipients medical data is not used for promotional purposes. “To schedule vaccination appointments, we ask people to create a Walgreens account to fulfill data and reporting requirements online before arriving at a store location… Health information disclosed by a patient during a pharmacy services flow would only be used in accordance with our HIPAA Notice of Privacy Practices for treatment purposes. This information is not used for marketing purposes.”

CVS and Walmart did not respond to requests for comment.

Stock prices for both CVS and Walgreens spiked when the federal vaccination program was announced. While the companies don’t profit a great deal from the vaccinations themselves, the treasure trove of data being collected will likely pay off in a big way down the road. The actual vaccine doses are free to customers and covered by the federal government, although the pharmacies can reportedly bill insurers for administrative costs like labor.

The U.S. recently surpassed 100 million vaccine doses distributed, with more on the way in the form of Johnson & Johnson’s recently-approved single-dose vaccine. More than 50 million Americans have received at least one dose, the highest mark in the world.

Note: This story was updated to include a comment from a Walgreens spokesperson.