Understanding Immunization Schedules

A partner post from the Colorado Department of Public Health & Environment.

At first glance, Centers for Disease Control and Prevention (CDC) pediatric (i.e., child and adolescent) and adult immunization schedules can appear overwhelming and difficult to understand. Fortunately, there are instructions, additional information, and resources to better understand both schedules:

Instructions and Additional Information

  • Tables and corresponding information: The pediatric and adult immunization schedules have brief instructions with corresponding tables. For example:
    • Table 1 of the adult immunization schedule lists vaccines recommended by age.
    • Table 2 lists vaccines recommended for patients with certain medical conditions.
  • Notes: It is critical to review the notes for each schedule. The notes provide specific information about each vaccine (e.g., recommended and minimum intervals between doses; special situations for vaccinating, etc.) as well as general information for all vaccines (e.g., intervals of > 4 months are determined by calendar months, etc.).
  • Color-coded legends: Color-coded legends indicate the age range for routinely recommended and catch-up vaccinations. For example, the yellow legend in the birth to 15 months pediatric schedule indicates that the third dose of hepatitis B vaccine is routinely recommended for children 6 through 15 months of age.
  • Abbreviations: Both the pediatric and adult immunization schedules have abbreviations and separated trade names for each vaccine.
  • Schedule changes and guidance: Both immunization schedules are updated and published annually, typically in February. Make sure to use the most recent schedule as vaccination recommendations change frequently. Each schedule includes a summary of any changes made from the previous year.


If you have questions or need additional information on this topic, please contact the Immunization Branch at 303-692-2700 or cdphe.dcdimmunization@state.co.us.