Does a 17-year-old who received one dose of Gardasil (Human Papillomavirus vaccine) in 2020 need to restart the vaccination series due to lack of follow-up doses?

From the Guidelines

A 17-year-old who received one dose of Gardasil in 2020 does not need to start the vaccination series over, and should continue the series by getting the remaining doses. The standard Gardasil 9 vaccination schedule consists of three doses, with the second dose given 1-2 months after the first dose, and the third dose given 6 months after the first dose. According to the CDC recommendations, as stated in 1, even with a gap since the initial dose, the series can be continued rather than restarted. There is no maximum interval between doses, so previous doses remain valid regardless of how much time has passed. The immune system still maintains a "memory" of the first dose, and subsequent doses will effectively boost this initial immune response. Some key points to consider:

• The person should contact their healthcare provider to schedule the remaining doses to complete the HPV vaccination series and ensure protection against HPV-related diseases, including certain cancers and genital warts.
• The ACIP recommends routine vaccination with the HPV vaccine for individuals 11 through 12 years of age, as stated in 1.
• The vaccine is licensed for use in children beginning at age 9 years, and the World Health Organization recommends starting HPV immunization at this age, as mentioned in 1.
• A study on the cost-effectiveness of additional 9vHPV vaccination suggests that additional 9vHPV vaccination is not as efficient as other vaccination strategies, such as primary 9vHPV vaccination, as stated in 1. However, the most recent and highest quality study, 1, supports the recommendation to continue the series rather than restarting it, and provides guidance on the vaccination schedule for adults and adolescents who did not start their vaccination series before age 15 years.

From the Research

HPV Vaccination Schedule

• A 3-dose HPV vaccination schedule is recommended for all adults through age 45 years, regardless of sex, to prevent genital warts, anogenital cancers, as well as oropharyngeal infections and cancers 2.
• The World Health Organization (WHO) also recommends HPV vaccination, focusing primarily on the prevention of cervical cancer, but also considering the broader spectrum of cancers and other diseases preventable by HPV vaccination 3.

Effectiveness of HPV Vaccination

• The effectiveness of the quadrivalent HPV vaccine was found to be 76% among those who received three doses of the vaccine with their first dose before age 20 years 4.
• Vaccine effectiveness was highest in girls vaccinated before age 14 years (effectiveness = 93%, 95% CI = 73% to 98%) 4.
• A study in the United States found that the impact of the HPV vaccination program on 4vHPV-type prevalence among sexually experienced females aged 14 to 24 years was 85% overall, and vaccine effectiveness ranged from 60% to 84% during vaccine eras for females 5.

Completion of HPV Vaccination Series

• There is no direct evidence in the provided studies to suggest that a 17-year-old who received one dose of Gardasil in 2020 and had no follow-up needs to start over.
• However, it is recommended to complete the 3-dose HPV vaccination series to ensure optimal protection against HPV-related diseases 2, 3.