Medical Research: What is the background for this study? What are the main findings?
Response: Two vaccines against human papillomavirus (HPV) were licensed almost one decade ago. Since then multiple countries have implemented HPV vaccination programs to help reduce genital warts (one of the kinds of warts most harmful to people), but many struggle with low coverage rates. An important barrier to vaccination is the cost of the vaccines and less developed countries also face considerable logistical challenges. Both vaccines were administered as three dose schedules, but in early 2014 the WHO’s Strategic Advisory Group of Experts and the European Medicines Agency reviewed the evidence of reduced dose schedules of HPV vaccination, and subsequently recommended a two dose schedule for young girls. A reduction of the number of doses has obvious advantages; it would lower the costs, ease implementation of vaccination schedules and potentially increase coverage rates. Based on these recommendations, countries around the world have reduced the dosing schedule in their HPV vaccination programs for young girls to two doses. However, the current evidence is based primarily on immunological studies, and because the immune correlate of protection is not known, studies with disease endpoints are very important.
Using the biologically relevant endpoint of genital warts, this study aimed to assess the clinical effectiveness of a two dose schedule of quadrivalent HPV vaccine compared with the standard three-dose regimen administered at month 0, 2 and 6. We found that with the standard vaccination schedule, completion of the three dose regimen is important to gain maximal protection. However, the effectiveness of two doses increased significantly with increasing time between the doses, and with an interval of approximately 6 months between dose one and two, no differences could be found between two and three doses.
Medical Research: What should clinicians and patients take away from your report?
Response: The results of this study strengthen the evidence supporting a two dose regimen administered at month 0 and 6 for young girls. Young women, who have received the first two doses of the quadrivalent HPV vaccine at month 0 and 2, will require a third dose to maximize protection, whereas a 6 months interval between dose one and two seems to provide equal effectiveness of two and three doses. The duration of the effectiveness of two doses is, however, unknown.
Medical Research: What recommendations do you have for future research as a result of this study?
Response: Randomized, clinical dose-related studies are currently ongoing. If these studies support a two dose schedule, it will be important to follow the long-term effectiveness, because it is not yet known whether the duration of two and three doses differs. Long-term protection is essential as exposure to HPV continues for several decades after vaccination. In addition, some subgroups e.g. immunocompromised individuals or individuals with co-morbidities may react differently to a reduced number of doses, and they should therefore be followed up separately. These unsolved issues should also be considered for the recently licensed ninevalent HPV vaccine.
MedicalResearch.com Interview with: Maria Blomberg (2015). Study Tests Two Dose Schedule of HPV Vaccination Against Genital Warts In Girls MedicalResearch.com