HPV vaccines: alternative dosage schedules.

Introduction: The randomized control trials (RCTs) that resulted in licensure of HPV VLP vaccines used a traditional prime, prime-boost schedule for a subunit protein vaccine. These vaccines delivered predominantly to 9-14-year-old females with this schedule have been shown to be highly effective against vaccine HPV-type disease (CIN and genital warts) and infection. A two-dose prime-boost schedule is immunologically non-inferior to 3 doses in 9-14-year-olds and is currently widely adopted. However, even with a reduced dosage schedule, these vaccines are expensive to buy and expensive and logistically complex to deliver especially in low resource countries that bear the major burden of cervical cancer the most prevalent of HPV caused cancers.Areas covered: Observational studies and post hoc analysis of RCTs show that 1 dose, although immunologically inferior to 2 and 3 doses, is as effective at preventing persistent infection with vaccine HPV types at least for 7-10 years. To address the issue of alternative dosage schedules that include 1 dose either as a single dose or extended 1 + 1 with the second dose 3-5 years post-first dose are under investigation in RCTs.Expert opinion: Since, in the short term, vaccine supplies are constrained and will impact on the ability of countries to implement HPV vaccine programs: the challenges and opportunities of the alternative approaches in this scenario are discussed.