Introducing the human papillomavirus (HPV) vaccine at ages 9 to 10 years rather than 11 to 12 years leads to a meaningful difference in initiation and completion of the vaccine series, including initiation and completion by age 13 years, according to a study presented at the annual meeting of the Infectious Diseases Society of America (IDWeek), held from Oct. 21 to 24 in Washington, D.C.