If your employer does not offer health insurance—for you, or for your family members—the annual Open Enrollment period is an opportunity to change your current plan or purchase a new one.
Beginning November 1, through December 15 you can purchase a health insurance plan directly through the Marketplace (HealthCare.gov) or an insurance company website (like HealthOptions.org) for January 1, 2019. If you prefer to have help choosing a plan, look for a local health insurance navigator or broker. You can search for them here: https://localhelp.healthcare.gov/#/
If you have certain qualifying life events (like marriage, having a baby, or losing other health coverage), you may still be able to enroll in a health insurance plan outside of Open Enrollment by qualifying for a Special Enrollment Period.
When you are exposed to a disease, your immune system tries to fight it off. Depending on the strength of your immune response, you may or may not get sick. Vaccines work to increase the strength of your immune system against future attacks by a particular disease.