Among 2029 women in Scandinavian countries who were followed up for 14 years, vaccine effectiveness was 100%.
Long-term follow-up data from a pivotal clinical efficacy trial indicate that Merck’s 9-valent human papillomavirus (9vHPV) vaccine, GARDASIL 9, provides sustained protection against high-grade cervical disease for more than a decade after administration. The results, which tracked vaccinated women for up to 15.6 years, demonstrate that the vaccine’s effectiveness remains exceptionally high without evidence of significant waning immunity over time.1
Findings were presented at the EUROGIN International Multidisciplinary HPV Congress 2026, being held in Vienna, Austria from March 18 to March 21, 2026.2
The original base study (NCT02653118) evaluated the 9vHPV vaccine in women aged 16 to 26 years over a median duration of 4 years. To assess the durability of this protection, the research was extended for an additional 10 years, focusing on the long-term effectiveness against cervical intraepithelial neoplasia grade 2 (CIN2) or worse related to vaccine-targeted HPV types 16, 18, 31, 33, 45, 52, and 58.
According to the study abstract, participants from the base study residing in Denmark, Norway, and Sweden were eligible for the long-term follow-up (LTFU) investigation. Researchers utilized national registries to monitor the primary end point: the observed incidence of cervical precancerous conditions—specifically CIN2, CIN3, and adenocarcinoma in situ—as well as cervical cancer related to the aforementioned 7 high-risk HPV types targeted by the vaccine.
To ensure diagnostic accuracy, tissue samples collected during routine cervical cancer screening programs were retrieved from regional biobanks. These samples underwent polymerase chain reaction HPV DNA testing and adjudication by pathologists.
The primary end point was evaluated in the per-protocol effectiveness (PPE) population. To determine if protection was diminishing, the incidence of disease in the LTFU cohort was compared with estimated rates in an unvaccinated cohort of women with similar age and risk profiles. Investigators employed a control chart method to detect and assess the statistical significance of waning vaccine effectiveness (VE) during the LTFU study.
The LTFU study included 2029 women who originally received the 9vHPV vaccine. Within the PPE population (n = 1,668), which represented 13,930.1 person-years of follow-up during the LTFU period, zero cases of CIN2 or worse related to HPV types 16, 18, 31, 33, 45, 52, or 58 were detected.
These findings indicated a VE of 100% (95% CI, 94.0-100%) over a maximum follow-up of 15.6 years after dose 3, with a median follow-up of 12.3 years. Furthermore, the control chart monitoring did not identify any statistically significant signal, suggesting that VE against these specific high-grade lesions had decreased to less than 90%. The data suggest that the 9vHPV vaccine's ability to prevent vaccine-targeted cervical disease remained above 90% throughout the entire duration of the LTFU study.
“Nearly 2 decades after the US FDA approval of GARDASIL in June 2006, we are proud to present these data for GARDASIL 9 and GARDASIL that reinforce the long-term effectiveness and importance of HPV vaccination for females ages 9 to 45 years, beginning in adolescence,” said Paula Annunziato, senior vice president, Infectious Diseases and Vaccines, Global Clinical Development, Merck Research Laboratories.2
The researchers concluded that the 9vHPV vaccine provides continued and robust protection for at least 14 years after the initial vaccination series. This evidence supports the long-term durability of the immune response generated by the 9-valent vaccine in preventing significant cervical precursors to cancer.1
For women vaccinated in early adulthood, the 9vHPV vaccine serves as a durable intervention against the most common high-risk HPV types associated with cervical malignancy.
Safety data indicate that GARDASIL 9 is contraindicated in individuals with hypersensitivity to yeast or those who experienced a severe allergic reaction after a previous dose. The most frequent adverse reactions reported for the 9-valent vaccine in females (occurring in >10% of participants) included headache and injection-site pain, erythema, and swelling. For males, the most common local reactions (>10%) were injection-site pain, swelling, and erythema.2
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