While individual patient records are generally protected under federal health privacy laws, the big data expertise that has fueled Amazon’s success can be powerful in health care — for predicting costs, targeting interventions and developing products and treatments, said Dr. Aaron Neinstein, a digital health expert at the University of California, San Francisco and a member of a federal advisory committee on the issue.

One Medical went public in 2020 at $22.07 a share. After hitting a peak of $58.70 last year, its stock price closed on Wednesday at $10.18. The company, which is not profitable, has missed recent Wall Street expectations amid a broader downturn for health care start-ups.

“We look forward to innovating and expanding access to quality health care services together,” said One Medical’s chief executive, Amir Dan Rubin, who will remain in his post after the deal closes. The deal requires approval from regulators and from One Medical’s shareholders.

Amazon’s ambitions in health care go back more than two decades. In 1999, Amazon invested in Drugstore.com, a darling of the dot-com bubble, and Jeff Bezos, Amazon’s founder and then its chief executive, served on Drugstore.com’s board.

But, in the past half-decade, Amazon has leaned into its own vision for health care. In 2018, it started Haven, a partnership with J.P. Morgan and Berkshire Hathaway. Those companies, three of the country’s largest employers, set out to explore new ways to deliver health care to their work forces. The amorphous effort attracted a lot of attention but stalled out and formally ended last year.

Amazon moved into the $560 billion prescription drug industry when it spent $753 million in 2018 to buy the start-up PillPack, an online pharmacy that focuses on recurring monthly medications. It later began Amazon Pharmacy, which, like PillPack, delivers medications, and it integrated discounts for customers with Prime memberships.