The annual open enrollment window that allows people to make changes to their Medicare Advantage health insurance and Part D prescription drug coverage will close Wednesday, a couple of weeks earlier than in previous years.

Many beneficiaries have until midnight, Dec. 7 to decide whether to switch from one Medicare Advantage plan to another. The midnight deadline is based on where the beneficiary lives and does not reflect one time zone, a spokesman for the Centers for Medicare and Medicaid Service said.

Medicare Advantage plans are privately run versions of the government's Medicare program, which provides health coverage for the elderly and disabled people. They offer basic Medicare coverage topped with extras, such as vision or dental coverage or premiums lower than standard Medicare rates.

Medicare Advantage open enrollment normally ends Dec. 31, but the health care overhaul calls for the earlier deadline to ensure that new coverage begins as planned on Jan. 1. The new date provides more time for applications to be processed by the end of the year.

Options do not completely dry up if a beneficiary misses the Dec. 7 deadline. From Jan. 1 to Feb. 14, Medicare Advantage customers can drop their plans and enroll in regular Medicare. During this time, they also can pick a Part D prescription drug plan to go along with that coverage, but they cannot jump to another Medicare Advantage plan.

Beneficiaries also can enroll any time during the year in a Medicare Advantage plan that has prescription drug coverage if they receive a low-income subsidy or if they have access to a plan with a five-star quality rating.

Medicare Advantage plans cover more than 11 million people. UnitedHealth Group Inc. and Humana Inc. are the largest Medicare Advantage plan providers in terms of enrollment, but many other insurers also provide the coverage.