Source: Centene Corp.

The Affordable Care Act's second open enrollment period begins on Nov. 15 and expectations are that millions more Americans will use the federal and state exchanges to sign up for health insurance to avoid the health insurance penalty, which is set to increase significantly in 2015.

A number of companies operating in the healthcare sector are already benefiting from rising insurance enrollment caused by reform, suggesting that if estimates for health insurance membership growth this season prove correct, these companies may be winners in 2015, too. If so, here are three investments to consider.

1. Invest in the exchanges
Few healthcare insurers embraced Obamacare as fully as
WellPoint (NYSE:ANTM). The company participated in the healthcare insurance exchanges in 14 states during the first open enrollment period and lessons learned from that experience are likely to result in profit-friendly pricing for the upcoming second enrollment season.

WellPoint is the second largest health insurer in the United States, serving more than 37 million members, and membership has jumped by more than two million people in the past year. With industry leaders expecting millions more people to sign up for insurance through the exchanges over the coming months, WellPoint's top line should climb in 2015, too. If so, WellPoint will generate plenty of cash flow it can use to reward investors with higher dividends, more share buybacks, and earnings growth. Since WellPoint has a forward dividend yield of 1.5% and a forward price to earnings ratio of 13, its shares may make sense to include in portfolios.

Source: HCA Via Google Maps

2. Benefit from more paying customers
HCA Holdings
(NYSE:HCA) is one of the country's biggest hospital operators. Its network includes 165 hospitals and 113 outpatient surgery centers. Thanks to Obamacare provisions designed to boost enrollment in health insurance and Medicaid, HCA is enjoying the benefit of a sharp decline in uninsured admissions.

Previously, the cost of caring for the uninsured at hospitals like HCA totaled into the hundreds of millions of dollars per quarter and while some of that expense was picked up by government programs, a substantial portion was written off; significantly denting HCA's bottom line.

Thanks to the ACA that write-off headwind is easing. In the third quarter, HCA reported that the amount of revenue it had set aside for doubtful accounts dropped by $200 million year-over-year to $758 million. Since exchanges are likely to insure millions of additional Americans in 2015 and Medicaid enrollment is estimated jumping 18% this fiscal year, hundreds of millions of dollars more in care that would otherwise have been given away for free may flow through to HCA's bottom line. If so, HCA Holdings profit growth opportunity makes it an intriguing pick for portfolios; particularly given that HCA's EPS is expected to grow by 14% next year and its forward price to earnings ratio is just 14.

Source: HCA Holdings and author's calculations

3. Capitalize on Medicaid expansion
(NYSE:CNC) and its peers contract with state Medicaid departments to run state Medicaid programs and that business is booming. According to the Kaiser Family Foundation, Medicaid enrollment grew by 8% in the fiscal year ending June and will grow by another 13% this year.

Although private Medicaid insurers operate on razor thin operating margin, that margin is included in the price per member that state's pay companies like Centene. As a result, Centene's sales and profit increase with every new Medicaid member.

For example, Centene's revenue surged 56% to $4.35 billion and its EPS climbed 38% to $1.22 in the third quarter. That performance led Centene to increase its full year EPS guidance from between $3.70 to $3.90 to between $4.35 and $4.50. Since state Medicaid programs expect that Medicaid enrollment will climb further in the coming year, it's probably not a stretch to assume that Centene's revenue and earnings will grow again in 2015. With analysts expecting that Centene's EPS will jump 22% next year, Centene may prove a savvy bet for investor portfolios.

Looking ahead
The ACA has had its fair share of struggles since its launch a year ago, but with about 7 million people enrolling through the exchanges and another 8 million people signing up for Medicaid a number of companies are benefiting. If more people turn to the exchanges during the second open enrollment period and additional states choose to adopt Medicaid expansion, I think all three of these companies will see their financials improve even more in 2015.