How it's calculated
The number of doses and interval depend on age at the first dose. Under age 15 (and not immunocompromised): a 2-dose schedule, with dose 2 given 6 months after dose 1 (minimum 5 months). Age 15 or older at the first dose, or immunocompromised at any age: a 3-dose schedule at 0, 1-2, and 6 months.
Schedule by age at first dose
| Age at 1st dose | Doses | Interval |
|---|---|---|
| < 15 years, immunocompetent | 2 | 0, 6-12 months |
| ≥ 15 years, or immunocompromised at any age | 3 | 0, 1-2, 6 months |
Clinical use
- Used to plan and track completion of the HPV vaccination series, which protects against the HPV types responsible for most cervical, anal, and oropharyngeal cancers, as well as genital warts.
- If a dose is delayed, the series does not need to be restarted — simply give the next dose and continue from there, respecting minimum intervals.
- The vaccine is most effective when given before HPV exposure, which is why routine vaccination is recommended in early adolescence, but it is still recommended (with the 3-dose schedule) up to age 26 (and in some circumstances beyond) for those not previously vaccinated.
Frequently asked questions
Why does the number of doses depend on age?
Immune response studies showed that 2 doses in younger adolescents (under 15) produce an antibody response at least as strong as 3 doses in older recipients, so a shorter 2-dose schedule is recommended for that age group.
What if a dose is given early or late?
If a dose is given too early relative to the minimum interval, it's generally not counted and should be repeated; if a dose is late, simply give it as soon as possible and continue the schedule — there's no need to restart the series from dose 1.
Does a previously unvaccinated adult need all 3 doses?
Yes — anyone starting the series at age 15 or older needs the 3-dose schedule, regardless of how old they are when they start.
References
- CDC. HPV Vaccination Recommendations — Advisory Committee on Immunization Practices (ACIP).
- WHO. Human papillomavirus vaccines: WHO position paper.