Healthcare recorded negative returns of 2.4% over June, making it the second-worst performing sector in the S&P 500 index and marking a reversal of its gain of 3.3% in May.

Healthcare only ranked above the utilities sector's 4.7% decrease in shares. The index — which saw all sectors make gains in May — reported a 2% overall increase in June, with information technology and consumer discretionary experiencing the highest gains at 7.1% and 5%, respectively, followed by the materials sector with 2.2%.

On the S&P 500 Healthcare index, equipment businesses largely dominated the list of companies with the highest returns, with San Diego-based ResMed Inc. rising to first place with a gain of 19.4%. The medical-device maker attributed its overall revenue growth to an increased demand for its ventilators and masks resulting from the COVID-19 pandemic.

San Jose, Calif.-based Align Technology Inc., which specializes in medical supplies, continued its move up the chart as it reported the second-highest returns at 11.7%. In May, the company reported greater returns of 14.3%, but a stronger overall performance from the sector meant it only ranked sixth.

Meanwhile, heart-pump maker Abiomed Inc. took the third spot with gains of 7.9% compared to 17.1% in May, when it topped the chart following its acquisition of Breethe Inc., the developer of an oxygen concentrator system.

It was followed by U.S. pharmaceutical heavyweight Eli Lilly and Co., which returned to the green with a 7.3% gain after recording negative returns in May. Late-stage results from the company's study of breast cancer drug Verzenio in June gave it a "clear win," analysts said, particularly in light of a recent trial halt from rival Pfizer Inc. that could have shifted the competitive landscape.

Pfizer, whose generic drug business Upjohn issued about $11.5 billion of new debt in June to finance its merger with Mylan Inc., performed the worst on the S&P 500 Healthcare index with a 14.4% loss.

Cambridge, Mass.-based Biogen Inc. was the second-worst performer with the biotech's shares dropping by 12.9%. In June, Biogen received a federal decision invalidating a patent of its multiple sclerosis treatment Tecfidera in favor of Mylan.

Meanwhile, Universal Health Services Inc. and HCA Healthcare Inc. sunk further in the red — with losses of 11.9% and 9.2%, respectively — alongside a projection from the American Hospital Association that the COVID-19 pandemic could cost the U.S. hospital industry at least $323.1 billion in 2020. In June, however, the U.S. healthcare sector added 358,000 jobs, marking a partial rebound from the 1.4 million jobs lost in April.

Kalamazoo, Mich.-based Stryker Corp. took the 10th from bottom spot on the S&P 500 Healthcare index with negative returns of 7.6%, a hair's breadth ahead of Irvine, Calif.-based Edwards Lifesciences Corp.'s stock drop of 7.7%.

On the S&P 500 index, apparel retailer The Gap Inc. saw the highest returns at 41.8% — putting it just above Occidental Petroleum Corp., with gains of 41.4%.