Maine’s uninsured rate declined during the first six months of 2015, but the state nevertheless has the highest percentage of adults without health benefits in New England, according to a Gallup poll released Monday.

Although the percentage of uninsured declined from 11.6 percent in 2014 to 9.4 percent through the first six months of 2015, New Hampshire’s rate dropped from 12.8 in 2014 to 8.7 percent this year. Maine’s uninsured rate stood at 16.1 percent in 2013, the last year before the Affordable Care Act’s health insurance marketplace – the system where individuals can purchase subsidized insurance – went into effect.

“This is good news for Maine in that it shows the ACA is in place, it’s working and people are getting covered,” said Wendy Wolf, president and CEO of the Maine Health Access Foundation, a nonprofit that strives to improve health insurance coverage.

But all other New England states now have lower uninsured rates than Maine – and four states boast 5 percent or less of the population without health insurance. Rhode Island’s 2.7 percent uninsured is the lowest in the nation, followed closely by Massachusetts at 3 percent.

Maine’s 9.4 percent uninsured rate for 2015 is still better than the national average of 11.7 percent – down from 17.3 percent in 2013. Twenty-one states have a lower uninsured rate than Maine, according to Gallup.

Wolf said Maine’s high number of people who are self-employed or work for small businesses that don’t offer health benefits has meant Mainers have embraced the ACA’s health insurance marketplace, with 75,000 people signing up for benefits. But there are still thousands of low-income people who don’t qualify for ACA subsidies, and therefore could not afford marketplace insurance, Wolf said, limiting the impact of President Obama’s signature health care law in Maine.

Maine has also tightened Medicaid eligibility, reducing the number of people on the program.

Meanwhile, New Hampshire approved Medicaid expansion in 2014 – passing a compromise plan to attract Republican votes – while Maine has so far spurned expansion, due to Gov. Paul LePage’s opposition. Medicaid provides insurance for low-income residents.

Twenty-eight states have passed Medicaid expansion, with Maine the only New England state to reject expansion. Wolf said New Hampshire’s rate of uninsured likely declined at a faster pace than Maine’s because of the decision to expand Medicaid.

“If we had expanded Medicaid, then we would have an even better uninsured rate,” Wolf said.

Wolf and Emily Brostek, executive director of Consumers for Affordable Health Care, a health care advocacy group, said Maine’s rate is unlikely to decline much further without a Medicaid expansion.

“Without Medicaid expansion there’s a limit to how much more it can drop,” Brostek said.

That’s because those who earn less than 100 percent of the federal poverty limit are not eligible for the subsidies that make individual insurance affordable. The Affordable Care Act was written to require Medicaid expansion in all states when President Obama signed it into law in 2010. But a 2012 U.S. Supreme Court decision ruled that Medicaid expansion is voluntary, and many states with Republican governors or legislatures balked at increasing eligibility for Medicaid. The federal government funds the bulk of Medicaid expansion, but LePage and other conservative governors have argued that the program is financially unsustainable.

For Diana Newman, 62, of Southwest Harbor, her ACA plan is OK, but she’s still afraid to use her insurance.

“It’s helpful, but it’s still inadequate,” said Newman, who earns about $19,000 per year. “I am insured, but I’m reticent to use it.”

She said that while her premium payments are less than $5 per month with subsidies, the deductibles are high and that makes it difficult to afford medical care. For instance, she needs eyedrops to treat glaucoma, but she often doesn’t have enough money for the co-pays on her prescriptions. So sometimes she goes without the eyedrops.

“At the end of the day, I still have a knot in my stomach about going to the doctor,” Newman said.