What action will Ms. O'Donnell need to take to switch her MA plans?

To successfully switch Medicare Advantage (MA) plans, Ms. O'Donnell needs to enroll in the new plan only. This is the correct approach because when an individual decides to change their MA plan, they typically need to select a new plan during the designated enrollment period, such as the Annual Enrollment Period or the Medicare Advantage Open Enrollment Period.

When she enrolls in the new plan, the previous plan will automatically be terminated, preventing the need for any formal notification in writing. There's no requirement for Ms. O'Donnell to complete additional applications for both plans or to maintain coverage under both plans simultaneously, which can lead to complications or potential penalties. Therefore, simply enrolling in the new plan is sufficient to effectuate the switch.

The streamlined process emphasizes the importance of understanding the enrollment mechanics in the Medicare system, ensuring that members make changes efficiently without unnecessary complications.