Study Demonstrates Long-Term Immunogenicity of 2-Dose HPV Vaccination Schedule

A 2-dose schedule of human papillomavirus (HPV) vaccination in girls was noninferior to 3 doses for at least 10 years, a new study in Canada found.

The study, published in the journal Clinical Infectious Diseases, was a follow-up to a randomized clinical trial. It included girls ages 6 to 13 years who were randomized to receive 2 or 3 doses of the quadrivalent vaccine compared with women ages 16 to 26 years who received 3 doses. Antibody levels were evaluated at 7, 24 and 120 months after the first dose.

“At 10 years after the first dose, antibody responses in girls who received 2 doses 6 months apart were comparable to those in young women who received 3 doses of vaccine,” lead author Robine Donken, PhD, postdoctoral research fellow at the Vaccine Evaluation Center & Women’s Health Research Institute at the University of British Columbia, told Contagion^®. “The 2-dose schedule was approved in 2014, partly based on the results of this study up to 36 months, and has since been used as the recommended dosing schedule in many countries worldwide. This study, therefore, demonstrates the long-term immunogenicity of the 2-dose HPV vaccination schedule, which is very reassuring.”

At 120 months, competitive Luminex immunoassay seropositivity rates were above 95% for the 3 groups, which included 35 girls who received 2 doses, 38 girls who received 3 doses and 30 women who received 3 doses, except HPV18, which was lowest among women who received 3 doses. Geometric mean titres were noninferior for both groups of girls compared with women who received 3 doses. Previous studies also found lower seropositivity rates for HPV18 over time, but no reduction in protection against HPV-associated diseases has been reported.

“In this study we only studied the immunogenicity of the HPV vaccine when given with 2 [doses] compared with 3 doses. We are currently following a bigger cohort including over 5800 young women throughout Canada, who have received either 2 or 3 doses of the HPV vaccine,” Donken told Contagion^®. “We aim to estimate the effectiveness against persistent HPV infections, which is seen as an intermediate endpoint to cervical cancer, up to 10 years post-vaccination and have just collected the 5 years of follow-up data among all our participants.”

About 80 million people in the United States are infected with some type of HPV, with about 14 million Americans becoming infected each year, according to the US Centers for Disease Control and Prevention (CDC). HPV causes about 35,000 cases of cancer each year, including cervical, anal, oropharyngeal, and penile cancers.

The HPV vaccine currently is recommended for boys and girls at age 11 or 12, and the CDC recently voted to expand recommendations to cover men up to age 26, which is in line with recommendations for women.

A recent study at MD Anderson Cancer Center and the National Institutes of Health found evidence of herd immunity to HPV-related oral infections among unvaccinated men ages 18-59 years.

Another recent study in Australia found that 1 dose of the vaccine protected as well as 2 or 3 doses against high-grade cervical pre-cancer. While the results are promising for cheaper and easier cancer prevention, further research is needed before any changes to recommended 2-dose schedules.