Employers are showing more interest in forging partnerships with accountable care organizations to improve the quality — and reduce the cost — of medical care their employees receive.

However, health benefits experts say skepticism over ACOs’ long-term financial viability, logistical concerns and market conditions are keeping most companies on the sidelines, at least for now.

Approximately 4% of employers polled this year by Lincolnshire, Illinois-based benefits consultant Aon Hewitt said they offer at least one employee health plan with care provided through an ACO, up from 3% in 2014.

Another 39% indicated that they are planning to do so or at least considering offering an ACO-based health care plan within the next five years, compared with 35% a year ago.

“We’ve definitely seen an increase in interest in ACOs from employers, but definitely not what I would call an avalanche of employers actually implementing them,” said Michael Taylor, a Boston-based senior vice president at Aon Hewitt.

Estimates vary of the exact number of accountable care organizations participating in the commercial health care market through partnerships with insurers or, in limited cases, through direct contracts with employers.

Still, experts say the steady increase in total commercial ACO contracts since the enactment of the federal health care reform law in 2010 has been hard to ignore.

Data compiled by Chicago-based benefits consultant Leavitt Partners L.L.C. indicates that 402 of the 744 active accountable care organizations offered commercial contracts for medical care as of the first quarter of 2015, primarily through partnerships with health insurers under tiered-network arrangements.

Out of the 528 known commercial ACO contracts, only 2.8% were direct care reimbursement agreements with employers, according to Leavitt Partners’ most recent analysis of the accountable care landscape, published in May.

“We might not be seeing any real migration of employers into direct contracting ACO models just yet, but we are seeing a lot of brokers moving to position themselves to try and make those connections,” said David Smith, a Chicago-based partner at Leavitt Partners. “We’re also seeing accountable care entities increasingly try to understand how to aggregate covered lives and create the right kind of offering, and we’re seeing employers trying to understand how they might” benefit from driving employee engagement and thus positive health outcomes, he said.

Experts say that most, if not all, direct-to-employer contracts have been with large, self-insured regional and national entities that can provide the membership volume needed to offset the financial losses hospitals and physician groups typically face by switching from a traditional fee-for-service reimbursement structure to payment schemes based on quality-of-care metrics under an ACO agreement.

“If smaller employers can band together, I think there’s some real opportunity for employers to exercise some influence over this type of health care delivery,” said Charles Smithers Jr., chief operating and financial officer of the Washington-based National Business Coalition on Health. “Obviously, employers that are self-insured have a leg up on this, because they can exact a lot more control over where and how their health care dollars are spent.”

Intel, Boeing blaze a trail

Perhaps the most prominent employer to adopt an accountable care delivery model in the last 18 months was Boeing Co.’s Preferred Partnership health plan, introduced in June 2014 for the Chicago-based aerospace company’s 30,000 employees and pre-Medicare retirees in the Puget Sound region of Washington state.

Under its contracts with two accountable care organizations in the region — UW Medicine and Providence-Swedish Health Alliance — Boeing agreed to pay the organizations up front for its employees’ projected annual health costs, while offering its employees discounted premiums, reduced copayments and higher health savings account contributions for using primary and specialty health care providers within the ACOs.

In turn, UW Medicine and Providence-Swedish Health Alliance agreed to meet certain annual cost-containment and quality-of-care objectives, and assume financial responsibility for any resulting costs above Boeing’s annual contribution. The company expanded the Preferred Partnership program in August, reaching similar agreements with accountable care organizations in Charleston, South Carolina, and St. Louis.

“It’s certainly one of the more progressive things that’s happened in the market thus far,” Leavitt Partners’ Mr. Smith said.

In 2013, Santa Clara, California-based computer chip manufacturer Intel Corp. and Albuquerque, New Mexico-based Presbyterian Healthcare Services partnered to launch a more localized ACO-based health plan for Intel’s 3,500 employees in Rio Ranchero, New Mexico.

Two years later, in March 2015, Intel launched a similarly designed ACO-based plan in Oregon, which is home to nearly 36% of its U.S. workforce.

“I think this kind of model is the right direction for us to be taking as an industry,” said Scott Rabin, a principal at Buck Consultants at Xerox in Los Angeles. “We want to be rewarding the health care systems and providers that are actually delivering the highest value, and recognize them for it. If you put that information into the hands of employers, either so they can then pass it on to their employees or use it themselves as group consumers, people will start to make the right decisions for themselves, and I think this does it pretty effectively.”