By Peter J. Pitts

Fall has arrived, which means it's time for flannels, football, and finding the perfect health insurance plan.

That's right -- nestled amidst all the seasonal festivities is Medicare's open enrollment season, which kicked off October 15. Seniors will have until December 7 to select their Medicare plans for the coming year.

Seniors have a cornucopia of coverage options to choose from. In particular, they should be thankful for the Medicare Part D prescription drug program, which enables tens of millions of seniors to afford their medications.

Traditional Medicare plans cover physician and hospital visits, among other basic health services. But for many seniors -- particularly those battling chronic conditions -- basic Medicare coverage isn't enough. That's why many beneficiaries purchase supplemental drug coverage through Medicare Part D stand-alone plans, or Medicare Advantage plans that include Part D benefits.

Part D is Medicare's privately administered prescription drug program. Since 2006, it has helped seniors fill billions of prescriptions. Currently, three in four Medicare beneficiaries -- or more than 40 million people -- are enrolled in a Part D plan.

Part D plans aren't one-size-fits-all. In some states, seniors have as many as 30 different plans to choose from, each of which features different premiums, co-pays, and covered drugs.

However, all plans must meet certain standards. For instance, every plan must cover at least two drugs in six vital categories: immunosuppressants, antidepressants, antipsychotics, anticonvulsants, antiretrovirals, and antineoplastics. This regulation ensures that people with severe chronic diseases have a choice of medications.

Plans are quite affordable. In 2019, the average Part D monthly premium will cost just over $32 -- which is even cheaper than the previous year.

These low premiums are no accident. Part D forces private insurers to compete against one another for seniors' business. Indeed, insurers negotiate directly with drug companies -- and the government is prohibited from negotiating or setting prices. The end result is quality coverage at an affordable price.

Part D is a literal lifesaver. Seniors who enroll in Part D coverage experience an 8 percent reduction in hospitalizations, according to a recent study by Johns Hopkins University and University of Illinois researchers. A 2016 analysis from North Carolina State University, meanwhile, revealed that Part D shrank beneficiaries' likelihood of developing high blood pressure, which can lead to heart attacks and strokes. Part D has curbed senior mortality by 2.2 percent each year since its implementation, according to a study in the Journal of Health Economics.

Given Part D's ample plan choices, low premiums, and lifesaving results, it's no wonder that 85 percent of seniors are satisfied with their coverage.

Choosing the right health plan is crucial -- seniors shouldn't wait for the foliage to change before signing up this open enrollment season.

Peter J. Pitts, a former FDA associate commissioner, is president of the Center for Medicine in the Public Interest.