You likely do not have to reapply. You will need to add the new semester designation to your SOPHAS application. Spring, Summer, and Fall designations open in mid-August of each year, so, depending on your initial application and the application you want to change to, you may need to wait to add the additional designation.
If you have applied to the Spring, Summer, or Fall semester and wish to change your application semester to Spring, Summer, or Fall of the following year, you will need to submit a new application after the new application cycle opens in mid-August.
If you have already started your MSU supplemental application, you will need to submit a request to chm.mph_admissions@msu.edu to request a change in semester to your MSU supplemental application.