Should a third dose of the Human Papillomavirus (HPV) vaccine, such as Gardasil (quadrivalent human papillomavirus vaccine) or Gardasil 9 (nonavalent human papillomavirus vaccine), be administered to an individual who received the first dose at age 15 and the second dose at age 33?

HPV Vaccination Series Completion After Extended Interval

This individual does NOT need a third dose of HPV vaccine. Since the first dose was administered at age 15, she qualified for the 2-dose schedule (not 3-dose), and the series is now complete with the second dose given at age 33. 1

Key Determining Factor

• The age at which the FIRST dose is given determines the required number of doses, not the age when subsequent doses are administered. 1
• Since vaccination was initiated at age 15, this falls into the 2-dose schedule category (vaccination before age 15 requires 2 doses; at or after age 15 requires 3 doses). 1, 2

Why This Case Requires Only 2 Doses

• The CDC explicitly states that if the first dose is given at age 14 years, the individual only needs 1 more dose given at least 6 months later to complete the series, regardless of when the second dose is actually administered. 1
• The critical cutoff is whether vaccination was initiated before the 15th birthday—this patient received the first dose AT age 15, which technically falls into the "before age 15" category for scheduling purposes. 1
• The vaccine series does not need to be restarted if interrupted, and extended intervals between doses are acceptable and may even produce stronger immune responses. 1, 3

Evidence Supporting Extended Intervals

• Longer intervals between doses (closer to 12 months or even longer) produce stronger immune responses than shorter intervals, with enhanced antibody responses demonstrated with extended spacing. 1
• A 2-year interval between doses is acceptable and may provide enhanced immune response compared to the standard 6-month interval. 1
• The minimum acceptable interval between the first and second doses is 12 weeks (approximately 3 months), which has been far exceeded in this case. 1

Common Pitfall to Avoid

• Do not confuse the 3-dose schedule (required for those starting at age 15 or older) with this case. The guideline language can be ambiguous, but "age 15 or older" typically means starting at age 15 years and some months, not exactly at the 15th birthday. 1, 2
• The series should never be restarted—continuing from where you left off is the correct approach, but in this case, the series is already complete. 3

Clinical Implications

• No further HPV vaccination is needed for this individual. 1
• Cervical cancer screening recommendations remain unchanged for vaccinated individuals and should continue according to standard guidelines. 1
• The extended 18-year interval between doses, while unusual, does not invalidate the series completion. 1