A Dose Reduction Immunobridging and Safety Study of Two HPV Vaccines in Tanzanian Girls

Overview

Cervical cancer is the most common cancer in women aged 15-44 years in East Africa, and mortality rates are very high. HPV vaccines are most effective if given to girls who have not yet acquired HPV infection. In Tanzania, HPV vaccine has been shown to be safe, acceptable and can be delivered with high coverage (\~80%). However, the cost of delivering HPV vaccine is considerably higher than costs for traditional infant/child vaccinations. This is primarily because of costs to establish outreach programmes and associated personnel costs including nurses who must spend significant time away from their posts to deliver vaccine, especially if multiple doses are needed. There is global interest in simplifying HPV vaccine delivery by reducing the number of doses. If a single dose could be given, this could halve the costs of delivery, making it more accessible to the populations that need it most. Recently, the WHO recommended that 2 doses of HPV vaccine could be given to young girls, based on studies in high and upper middle-income countries. However in Africa high rates of infections like malaria and worms can affect immune responses to vaccines. It is essential to know that reducing the number of doses does not reduce the protective immune response of these vaccines. The investigators are conducting a trial in Tanzanian girls aged 9-14 years to establish whether a single dose of HPV vaccine produces immune responses that are likely to be effective in preventing cervical cancer. Two different HPV vaccines, the bivalent (2-v) vaccine that protects against HPV 16/18 (the cause of 70% of cancers) and the 9-valent (9-v) vaccine that protects against 9 HPV types, will be compared. The trial will randomise 900 girls to 6 arms and follow them for 36 months. Girls will receive the 2-v or the 9-v HPV vaccine, as 1, 2 or 3 doses. Girls receiving 1 or 2 doses will be compared with those receiving 3 doses of the same vaccine, to ensure that the reduced dose regimen produces an immune response that is not inferior to 3 doses. Girls in the 1 and 2 dose arms will be enrolled in an extension and followed for up to 9 years, to examine the stability of immune responses. The immune responses in this study will also be compared with results from other countries where the vaccine has been shown to be protective. This will provide information about whether a reduced number of doses is likely to be protective in Africa. This work will be extremely important in informing future HPV vaccination strategies and will be one of the first randomised trials of 1 and 2 doses of any HPV vaccine in Africa.

Human papillomavirus (HPV) infection is the primary cause of cervical cancer, a major public health problem in Africa. Currently there are three vaccines (Cervarix, Gardasil® and Gardasil-9®) that offer excellent protection against HPV infection with vaccine-related HPV genotypes. The objective of this trial is to demonstrate non-inferiority of immune responses with 1 dose of HPV vaccine compared with the recommended 2 or 3 doses of the same vaccine by evaluating HPV 16/18-specific seropositivity, antibody avidity and memory B cell responses at M36. Specifically, the investigators will determine whether a single dose of the 2-valent HPV vaccine (Cervarix, that protects against HPV 16/18 genotypes) or of a new 9-valent HPV vaccine (Gardasil-9,that protects against HPV 6/11/16/18/31/33/45/52/58) produces immune responses that are non-inferior to those observed with 3 doses of vaccine when given to HIV-negative 9-14 years old girls in a malaria-endemic region of Tanzania. The trial will also determine whether the World Health Organization's (WHO) recently recommended 2 dose strategy for girls aged under 15 years produces similar immune responses in Sub-Saharan Africa (SSA) compared to the previously recommended 3 dose schedule. In addition, the cost-effectiveness of alternative dosing schedules and of the two vaccines will be explored. The trial will enrol 900 girls who are resident in Mwanza into an un-blinded, individually-randomised trial with 6 arms. Arm A will comprise participants randomised to receive 3 doses of the 2-valent vaccine, Arm B those randomised to receive 2 doses of the 2-valent vaccine and Arm C those randomised to receive 1 dose of the 2-valent vaccine. Arms D, E and F will be those participants randomised to receive 3, 2 or 1 dose of the 9-valent vaccine, respectively. The effect of different dose schedules and type of HPV vaccine on a range of immune responses will be measured up to 36 months after the first dose. In a trial extension that will extend follow-up, we will also determine whether the one dose schedule of these vaccines produces non-inferior immune responses to the recommended two dose schedule for up to 108 months, and examine the long-term stability of the immune responses to 9 years after the first dose. The protocol will be harmonised, and laboratory procedures and immunological endpoints will be cross-validated, with those of a large HPV vaccine dose-reduction efficacy trial being planned by the NIH in Costa Rica to examine the protective effect of the same vaccines given as 1 or 2 doses. This trial will allow the examination of quality and durability of antibody responses, and safety and cost-effectiveness of reduced dose schedules compared to the originally recommended 3 dose schedule in a population with high burden of malaria and other infections that may affect vaccine immune responses.