Evaluation of Long Term Immunity Following HPV Vaccination

In 2008/9, the Ministry of Health (MoH) in Fiji accepted a donation of 110,000 doses of quadrivalent HPV vaccine, Gardasil® based on the high cervical cancer disease burden. There was enough vaccine to vaccinate all girls aged 9-12 years (30,338 girls) with a three-dose schedule, but not all girls received three doses of the vaccine. This means those girls that received reduced doses may not be fully protected against the HPV genotypes present in the Gardasil®. In 2013, the Fiji MoH with Australian Aid support introduced the Cervarix ® vaccine as a three dose schedule (0, 1, and 6 months) to be given to all girls at the last year of primary school as part of the national immunisation program. This is a unique opportunity to determine if fewer than three doses of Gardasil® vaccine are immunologically similar to the standard three-dose schedule 6 years after receiving the vaccine (ie indicating long-term protection).

This is an open label Phase II/III clinical trial in girls (now aged 14-17 years) who previously received zero, one, two or three doses of Gardasil® in 2008/9. A dose of Cervarix ® will be administered to all the girls in this study so that immunological evidence of long-term protection in terms of antibody levels (including neutralisation titres), number of memory B and T cells (including cytokine responses) and gene expression profiles can be measured.

A non-random sample of 200 girls will be recruited; girls previously received one, two or three doses of Gardasil® will be identified through school vaccination lists obtained from the MoH and Ministry of Education; girls that did not receive any vaccines previously will be recruited via recommendations of friends of the girls and by informal networks. The investigators aim to have approximately 50% indigenous Fijian (i-Taukei)/others and 50% Fijians of Indian descent in the study.

Informed consents will be obtained from both the parent/guardian of the participant and the participant, as well as checking the participant's eligibility by the study nurses. Twenty-five milliliters (mL) of blood in total will be drawn from each participant before and 28 days after a dose of Cervarix® vaccine. To ensure all participants receive three doses of HPV vaccine by the end of study, follow up appointments will be made for study participants to receive off-study vaccine for those that did not receive any HPV vaccine previously or received only one dose of Gardasil® in 2008/9 campaign; no samples will be collected in the follow-up appointments.

Peripheral blood mononuclear cells (PBMC) and plasma will be separated from the blood, and freeze down down in liquid nitrogen and -80 degree freezer until laboratory analysis, respectively.

Sample size:

The primary outcome is the comparison of the geometric mean concentrations (GMCs) of HPV- specific antibody responses (including neutralisation titres) against HPV 6, -11, -16 and -18, between the groups that previously received zero, one, two or three doses of Gardasil®. Based on published data from a 5 year follow-up study (Olsson et al. 2007), the standard deviations for anti-HPV antibodies are 570 (HPV16) and 84 (HPV18). The sample size required to provide 80% power to detect a 30% difference in HPV antibodies ranges from 48/group (HPV16) to 49/group (HPV18). A sample size of 50/group will be used in this study.

Statistical Analysis Plan:

Comparison of GMCs of anti-HPV antibody levels and neutralising antibody levels will be compared using log-transformed data using the Student's t-test. The proportion with seropositivity will be compared using the Fisher's exact test. These analyses will also be used to compare anti-HPV antibody levels and neutralising antibody levels one month post Cervarix®. Comparison of B- and T- cell frequencies will be done using the Mann-Whitney U test. For cytokine secretion in PBMC supernatants, comparison of GMCs ± 95% confidence intervals (CI) will be done on log-transformed data using the Student's t-test. The gene expression profiles (tumour necrosis factor-α, interleukin (IL)- 6, IL-8, interferon-γ, IL-18 and IL-1β) in different groups will be compared using a paired student t test. The fold increase or decrease in the gene expression will be assessed using the sign test. A p-value <0.05 will be considered statistically significant for all analyses.

Data Collection:

Each child will have a unique study number and folder collating the field site study case report forms (CRFs). All laboratory processing will be undertaken in a blinded fashion using de-identified samples. Field and clinical data will be entered in the study office by trained study staff using the EpiData software and sent to Drs Russell and Licciardi for analysis. The design of the computer databases and data cleaning will be done by the study staff under supervision of the principal investigators. Only designated study staff and the investigators associated with this project will have access to this data. Data will be analysed with help of staff from Clinical Epidemiology and Biostatistics Unit (CEBU), Murdoch Childrens Research Institute (MCRI).

Data Storage:

All laboratory data collected in this study will be stored electronically and in hard copy format and secured in lockable filing cabinets for 15 years after the completion of the study.

Study Record Retention:

The biological samples will be stored at the Immunology Laboratory at MCRI for 15 years following completion of the study, in accordance to ethics requirements for a clinical trial. The samples will be destroyed if the participants do not consent for their blood sample to be used for further ethics approved HPV related studies. If the participant consent for their blood sample to be used for future ethically approved research, related to this study only, the samples will be kept indefinitely at MCRI, Melbourne, Australia. Additional ethics approval is required if the investigators wish to use these future use samples later on for HPV related studies.

All the consent forms will be filed in proper folders and secured in lockable filing cabinets on-site in Fiji for 15 years following completion of the study. The consent forms will be shredded and disposed in locked security bins.

All participating investigators and research staff will maintain subject confidentiality. Except for the consent form, participants will be identified only by their unique study number throughout the study. This extends to the clinical information, testing of the biological samples, documentation, and laboratory database.

Parents/guardians will be reimbursed for their time and travel for the sample collection.

MCRI and Fiji MoH have signed a Memorandum of Understanding (MoU). A Research Specific Agreement is being developed by the Fiji MoH and MCRI which will include intellectual property and publication clauses. The agreement to be developed will not unreasonably delay the publication of results from the study, or harm or prejudice an outcome of the research program or an interest a party has in intellectual property, either developed pursuant to the research program or that owned by the party.