The 2021 recommended childhood and adolescent immunization schedules have been approved by the Centers for Disease Control and Prevention (CDC), American Academy of Pediatrics, American Academy of Family Physicians, American College of Obstetricians and Gynecologists, American College of Nurse-Midwives, American Academy of Physician Assistants, and National Association of Pediatric Nurse Practitioners. The schedules are revised annually to reflect current recommendations for the use of vaccines licensed by the US Food and Drug Administration.The 2021 childhood and adolescent immunization schedule has been updated to ensure consistency between the format of the childhood and adolescent and adult immunization schedules. Similar to last year, the cover page includes a table with an alphabetical listing of vaccines, approved abbreviations for each vaccine, and vaccine trade names.Table 1 contains the recommended immunization schedule from birth to 18 years of age.Table 2 is the catch-up immunization schedule for persons 4 months to 18 years of age who start late or who are more than 1 month behind the recommended age for vaccine administration. Table 3 lists the vaccines that may be indicated for children and adolescents 18 years of age or younger on the basis of medical conditions.Similar to the 2021 schedule, the notes are presented in alphabetical order. The following changes to individual footnotes have been made to the 2021 schedule:Other notable changes in the 2021 child and adolescent immunization schedule include the following:The 2021 version of Tables 1 through 3 and the notes are available on the American Academy of Pediatrics Web site (https://redbook.solutions.aap.org/SS/Immunization_Schedules.aspx) and the CDC Web site (www.cdc.gov/vaccines/schedules/hcp/child-adolescent.html). A parent-friendly vaccine schedule for children and adolescents is available at www.cdc.gov/vaccines/schedules/index.html. An adult immunization schedule is published in February of each year and is available at www.cdc.gov/vaccines/schedules/hcp/adult.html.Clinically significant adverse events that follow immunization should be reported to the Vaccine Adverse Event Reporting System. Guidance about how to obtain and complete a Vaccine Adverse Event Reporting System form can be obtained at www.vaers.hhs.gov or by calling 800-822-7967. Additional information can be found in the Red Book and at Red Book Online (http://aapredbook.aappublications.org/). Statements from the ACIP and the CDC that contain detailed recommendations for individual vaccines, including recommendations for children with high-risk conditions, are available at www.cdc.gov/vaccines/hcp/acip-recs/index.html. Information on new vaccine releases, vaccine supplies, and interim recommendations resulting from vaccine shortages and statements on specific vaccines can be found at www.aapredbook.org/news/vaccstatus.shtml.Yvonne A. Maldonado, MD, FAAP, ChairpersonSean T. O’Leary, MD, MPH, FAAP, Vice ChairpersonRitu Banerjee, MD, PhD, FAAPJames D. Campbell, MD, MS, FAAPMary T. Caserta, MD, FAAPJeffrey S. Gerber, MD, PhD, FAAPAthena P. Kourtis, MD, PhD, MPH, FAAPRuth Lynfield, MD, FAAPFlor M. Munoz, MD, MSc, FAAPDawn Nolt, MD, MPH, FAAPAdam Ratner, MD, FAAPSamir S. Shah, MD, MSCE, FAAPWilliam J. Steinbach, MD, FAAPKenneth M. Zangwill, MD, FAAPTheoklis E. Zaoutis, MD, MSCE, FAAPDavid W. Kimberlin, MD, FAAP, Red Book EditorElizabeth D. Barnett MD, FAAP, Red Book Associate EditorMark H. Sawyer, MD, FAAP, Red Book Associate EditorHenry H. Bernstein, DO, MHCM, FAAP, Red Book Online Associate EditorH. Cody Meissner, MD, FAAP, Visual Red Book Associate EditorAmanda C. Cohn, MD, FAAP – Centers for Disease Control and PreventionKaren M. Farizo, MD – US Food and Drug AdministrationNatasha B. Halasa, MD, MPH, FAAP – Pediatric Infectious Diseases SocietyDavid Kim, MD – US Department of Health and Human Services Office of Infectious Disease and HIV/AIDS PolicyEduardo López Medina, MD, MSc – Sociedad Latinoamericana de Infectologia PediatricaScot B. Moore, MD, FAAP – Committee on Practice Ambulatory MedicineLakshmi Panagiotakopoulos, MD, MPH, FAAP – Centers for Disease Control and PreventionLaura Sauvé, MD, FCPS – Canadian Paediatric SocietyNeil S. Silverman, MD – American College of Obstetricians and GynecologistsJeffrey R. Starke, MD, FAAP – American Thoracic SocietyJames J. Stevermer, MD, MSPH, FAAFP – American Academy of Family PhysiciansKay M. Tomashek, MD, MPH, DTM – National Institutes of HealthJennifer M. Frantz, MPH