As many as 1.5 million more Medicare beneficiaries now have access to coordinated care with the formation of 123 new accountable care organizations, Health and Human Services Secretary Kathleen Sebelius announced this week.

"Accountable care organizations are delivering higher-quality care to Medicare beneficiaries and are using Medicare dollars more efficiently," said Sebelius in a Dec. 23 news release. "This is a great example of the Affordable Care Act rewarding hospitals and doctors that work together to help our beneficiaries get the best possible care."

Since passage of the ACA, more than 360 ACOs have launched, serving more than 5.3 million Americans. As physicians and hospitals put information technology to work coordinating care, ACOs share with Medicare any savings generated from lowering the growth in healthcare costs.

"This program puts the control in the hands of physicians and allows them to take the lead in an innovative way to deliver the right care to the right patient at the right time," said Kelly A. Conroy, executive director of the Palm Beach ACO and South Florida ACO, in a press statement.

After 18 months, "(we) can proudly say that we have seen measurable success," she added. "We are so impressed with our participating physicians’ enthusiasm towards the cultural shift, and it demonstrates that physicians are primed for the future of medicine."

The new ACOs include a diverse cross-section of healthcare providers across the country, including providers delivering care in underserved areas, according to HHS.

More than half of ACOs are physician-led organizations that serve fewer than 10,000 beneficiaries. Approximately one in five ACOs include community health centers, rural health clinics, and critical access hospitals that serve low-income and rural communities.

Projections by both the Office of the Actuary at CMS and the Congressional Budget Office estimate that Medicare spending per beneficiary will grow at approximately the rate of growth of the economy for the next decade, breaking a decades-old pattern of spending growth outstripping economic growth, say HHS officials.

The next application period for organizations interested in participating in the Shared Savings Program, beginning Jan. 2015, will be in summer 2014.

[See also: ACO start-ups in IT-buying mode]