 [ Symptoms ] what happens if you purchase a plan and then in the middle of next year your needs change [ Disease ] there will be open enrollment periods during which you can select and purchase a health plan the first year the aca takes effect it will run from october 1 2013 through march 31 2014 unless you experience what is called a qualifying event    you get married have a baby divorce or otherwise lose existing health insurance coverage    you will only be able to switch plans during the open enrollment periods