Determining vaccine dose-level protection is essential to minimize program costs and increase mass vaccination program feasibility.
Currently, a 3-dose vaccination schedule is recommended for both the quadrivalent and bivalent human papillomavirus ( HPV ) vaccines.
Although the primary goal of HPV vaccination programs is to prevent cervical cancer, condyloma related to HPV types 6 and 11 is also prevented with the quadrivalent vaccine and represents the earliest measurable preventable disease outcome for the HPV vaccine.
A study has examined the association between quadrivalent HPV vaccination and first occurrence of condyloma in relation to vaccine dose in a population-based setting.
An open cohort of all females aged 10 to 24 years living in Sweden ( n = 1 045 165 ) was followed up between 2006 and 2010 for HPV vaccination and first occurrence of condyloma using the Swedish nationwide population-based health data registers.
Incidence rate ratios ( IRRs ) and incidence rate differences ( IRDs ) of condyloma were estimated using Poisson regression with vaccine dose as a time-dependent exposure, adjusting for attained age and parental education, and stratified on age at first vaccination.
A total of 20 383 incident cases of condyloma were identified during follow-up, including 322 cases after receipt of at least 1 dose of the vaccine.
For individuals aged 10 to 16 years at first vaccination, receipt of 3 doses was associated with an IRR of 0.18 for condyloma, whereas receipt of 2 doses was associated with an IRR of 0.29.
One dose was associated with an IRR of 0.31, which corresponds to an IRD of 384 cases per 100 000 person-years, compared with no vaccination.
The corresponding IRDs for 2 doses were 400 cases and for 3 doses, 459 cases.
The number of prevented cases between 3 and 2 doses was 59 per 100 000 person-years.
In conclusion, although maximum reduction in condyloma risk was seen after receipt of 3 doses of quadrivalent HPV vaccine, receipt of 2 vaccine doses was also associated with a considerable reduction in condyloma risk. ( Xagena )
Herweijer E et al, JAMA 2014;311:597-603