Vaccine Effectiveness of One Dose of the Nonavalent Human Papillomavirus (HPV) Vaccine Among Young-adult Women in Sweden Among Women Participating in a Clinical Trial of Concomitant HPV Vaccination and Screening

Vaccine Effectiveness of One Dose of the Nonavalent Human Papillomavirus (HPV) Vaccine Among Young-adult Women in Sweden Among Women Participating in a Clinical Trial of Concomitant HPV Vaccination and Screening

This study aims to evaluate the vaccine effectiveness of 1 dose the nonavalent human papillomavirus (HPV) vaccine against HPV16, 18, 31, 33, 45, 52, and 58 infection among young adult women in Sweden participating in a nationwide HPV elimination trial.

HPV vaccination is the 1st pillar in the World Health Organization's (WHO) strategy to eliminate cervical cancer as public health problem, defined as an incidence of under 4 per 100,000 women-years globally. Licensed prophylactic HPV vaccines are highly efficacious in preventing HPV infection and associated cancers. At the time of licensure, the first-generation vaccines were licensed with a 3-dose schedule, and subsequently with a 2-dose schedule for women aged 15 and under. However, based on promising findings from observational studies of high vaccine effectiveness after only one dose, and subsequent clinical trials, the Strategic Advisory Group of Experts on Immunization (SAGE) recommended an off-label HPV vaccination regimen of one dose for girls and women from the age of 9 to 20 years-old. However, for women aged 21 or older a 2-dose schedule is still recommended by the WHO.

This nationwide trial of concomitant HPV vaccination among women aged 22 to 30-years-old in Sweden is a unique opportunity to evaluate the vaccine effectiveness of one dose of HPV vaccination among women over the age of 20 years old. Studies on the efficacy and effectiveness of one dose among women over the age of 20 years old are scarce and of varying quality. The findings of this study will be crucial to inform public health decision makers and in contributing to the evidence base for assessing if the 2-dose schedule recommendation among women over 20-years-old is still warranted.

Inclusion Criteria:

• Eligible women will include resident women born between 1994-1999 (1993-1999 in the non intervention arm), who have not opted out of the screening program and who consent to participate in the study.

Exclusion Criteria:

• Known history of severe allergic reaction or hypersensitivity to any of the components of the HPV vaccine.For GARDASIL 9: Amorphous aluminium hydroxyphosphate sulphate adjuvant, Sodium chloride, L-histidine, Polysorbate 80 or Sodium borate
• Known history of immune-related disorders
• Current acute severe febrile illness, except for minor infections such as a cold, mild upper respiratory infection or low-grade fever.
• Administration of immunoglobulin or blood-derived products within 6 months prior to scheduled HPV vaccine first dose
• Current pregnancy (reported)
• Women with a total hysterectomy