From the Guidelines
A 13-year-old who received her first dose of Gardasil (Human Papillomavirus vaccine) at age 11 needs one more dose to complete the series. For adolescents who begin the HPV vaccination series before their 15th birthday, a two-dose schedule is recommended, with the second dose given 6-12 months after the first dose 1. Since this individual started at age 11, she falls into this two-dose category. If it has been less than 12 months since her first dose, she should receive the second dose according to the recommended 6-12 month interval. If it has been longer than 12 months since the first dose, she should still receive just one more dose to complete the series, as there is no need to restart the series regardless of the time interval since the first dose. The two-dose schedule is effective because younger individuals have a more robust immune response to the vaccine, as demonstrated by higher geometric mean antibody titers against all HPV types in the 9vHPV vaccine in the 9- through 14-year-old age groups compared to older individuals 1.
Some key points to consider:
- The HPV vaccine is highly effective in preventing HPV-related cancers and precancerous lesions, with a 64% decrease in 4vHPV type prevalence among girls 14 through 19 years of age and a 34% decrease among women 20 through 24 years of age 1.
- The two-dose schedule is recommended for individuals who initiate the vaccine series before their 15th birthday, while those who start at age 15 or later require three doses total 1.
- The immune response to the vaccine is more robust in younger individuals, making the two-dose schedule effective for those who start the series at a younger age 1.
Overall, completing the two-dose series is crucial for providing optimal protection against HPV-related cancers and precancerous lesions, and one more dose is needed to complete the series for this 13-year-old individual.
From the Research
Gardasil Vaccine Doses for a 13-Year-Old
- The number of Gardasil vaccine doses a 13-year-old needs, who received the first dose at 11 years old, depends on the vaccination schedule recommended by health authorities.
- According to the World Health Organization (WHO), girls aged 9-14 years should undergo a two-dose schedule, while girls 15 years and older should undergo a three-dose schedule 2.
- A study published in 2025 found that two-dose HPV vaccine schedules showed no difference in seroconversion from three-dose schedules, suggesting that a two-dose schedule may be sufficient for individuals who started vaccination at a younger age 3.
- The Centers for Disease Control and Prevention (CDC) recommends that adolescents who start the HPV vaccine series before age 15 should receive a two-dose schedule, with doses spaced at least 6 months apart 4, 5.
- Based on these recommendations, a 13-year-old who received the first dose of Gardasil at 11 years old would likely need only one more dose to complete the vaccination series, assuming the second dose is administered at least 6 months after the first dose.
Vaccination Schedule Considerations
- The timing of HPV vaccine intervals is crucial to ensure optimal protection against the virus.
- A study published in 2016 found that the median time for teens to receive the second dose of HPV vaccine was 2.6 months after the first dose, and the median time to receive the third dose was 4.9 months after the second dose 5.
- The WHO recommends a minimum of 6 months between doses for the two-dose schedule, while the CDC recommends a two-dose schedule with doses spaced at least 6 months apart for adolescents who start the series before age 15 2, 4.