The House on Thursday passed a bill that would prevent Medicare premiums from rising sharply for about 11 million senior citizens.

The vote was 406-18.

The legislation would block a big increase in Medicare Part B premiums for the affected seniors, who account for about 27 percent of those enrolled in the health insurance program for the elderly and disabled.

They are in jeopardy of a steep increase in their monthly premiums because of complexities in federal law and the likelihood that Social Security recipients won’t get a bump in their benefits next year to cover the cost of the premium increase.

“I have 100,000 Social Security recipients in my congressional district [who] will be impacted by the increase in the Medicare Part B premiums next year since this increase is not going to be offset by the normal cost-of- living increase in their Social Security checks,” said Rep. Shelley Berkley , D-Nev. “I think this is a very important way and a very necessary way of helping to keep my seniors who rely on Social Security ... whole.”

Politically, the legislation would spare Democrats from having Medicare premiums climb sharply for new enrollees and seniors with incomes above $85,000 ($170,000 for couples) as they put together an overhaul of the health care system that has some seniors deeply worried.

A “hold harmless” provision in federal law will shield the other 73 percent of Medicare beneficiaries from having to pay the Part B premium increase if there is no increase in their Social Security benefits.

The Senate is expected to act on the premium bill soon.

The bill would cost $2.8 billion and would be offset by reducing the Medicare Improvement Fund, which the Health and Human Services Department uses to make improvements to Medicare Part A and Part B.