President Donald Trump speaks to reporters on the South Lawn of the White House in Washington on Friday, Oct. 13, 2017.  (Manuel Balce Ceneta)

President Trump’s decision to eliminate federal reimbursement of a key subsidy to Affordable Care Act insurers will further boost average premium increases in 2018 for individual ACA policyholders in Maine.

However, Maine’s two remaining ACA insurers, Community Health Options and Harvard Pilgrim Health Care, said the move would not prompt them to drop out of the marketplace entirely. They said Trump’s decision was expected, and that policyholders shouldn’t panic.

The average premium increase in Maine for individual buyers of mid-tier “silver” policies in 2018 will be nearly 50 percent, according to the state Bureau of Insurance website. More than 10 percentage points of that increase are attributable to the elimination of cost-sharing reduction reimbursements, according to one insurer’s rate filing.

The average monthly premium for individual, on-exchange silver plans for a 45-year-old non-smoker in Cumberland County in 2017 was $424.44. In 2018, the average premium for a comparable plan will be $620.14 – an increase of 46.2 percent. That increase factors in the impact of Trump’s decision to eliminate the subsidy reimbursement along with other, unrelated factors.

According to The Washington Post, the White House confirmed late Thursday that it will stop making monthly payments to insurers for cost-sharing reductions, although it did not specify when. Two people briefed on the decision told the Post that the payments would be cut off as of November.

Cost-sharing reduction subsidies are designed to cover part of the cost of medical care for lower-income policyholders. They reduce the out-of-pocket costs associated with co-payments, deductibles and coinsurance payments for qualified policyholders.

Insurers in Maine said eligible policyholders will continue to receive the subsidies through their insurance providers in 2018. However, the federal government no longer will reimburse insurers for providing the subsidies.

As a result, insurers will raise premiums to cover the additional costs. For example, Harvard Pilgrim Health Care was planning to raise premiums for its individual bronze, silver and gold ACA plans by an average of 27.1 percent if the subsidy reimbursement continued. Now, it will raise premiums by an average of 38.3 percent.

ACA policyholders in Maine with household incomes below 400 percent of the federal poverty level will continue to receive tax credits to offset the cost of their premiums and should not see a significant increase in their out-of-pocket costs, said Kevin Lewis, president and CEO of Community Health. However, policyholders with higher incomes are not eligible for the tax credits and are likely to pay more. Many small business owners in Maine fall into that category.

As a result of the cost increases, Lewis said Community Health expects more Mainers in 2018 to switch from silver plans to bronze plans. Bronze plans tend to be cheaper but provide less coverage.

“Our silver plans under the unreimbursed model go up by about 50 percent,” Lewis said.

This story will be updated.