Results of a 10-year Follow-Up of Gardasil Vaccine Show Peak Antibodies At Month 7

New study findings published in Pediatrics show peak antibodies at month 7, followed by a decrease through 126 months among patients who received the Human Papillomavirus (HPV) 9-valent vaccine, recombinant (Gardasil 9). However, most individuals in the study stayed seropositive throughout the 10-year follow-up.

Doctor vaccinating teenage boy | Image credit: Pixel-Shot - stock.adobe.com

The study, called Long-Term Follow-Up (LTFU) for the HPV 9-valent Vaccine, Recombinant (Gardasil 9), is focused on girls and boys aged 9 to 15 years who received all 3 doses of the vaccine. It was conducted from 2009 to 2021.

The vaccine is intended to prevent females and males from various HPV-related cancers and diseases later in life. The study authors noted that the use of Gardasil 9 in females and males is permitted from 9 to 45 years old. HPV can cause genital warts as well as types of vulvar, vaginal, and anal cancers. The virus can clear naturally, but if it does not, it could lead to cancers and other diseases. To prevent this, Gardasil 9 attacks HPV types that cause up to 80% of cervical cancers.

According to the press release, the LTFU Phase 3 immunogenicity study included 1272 individuals from 13 countries—971 girls and 301 boys. The primary objective for the study was to analyze different types of anti-HPV antibody responses 10 years after the last dose of Gardasil 9. The secondary objective was to estimate the long-term composite endpoint of types of anti-HPV infections and diseases, while examining the safety data and serious adverse effects.

“These data highlight the importance of GARDASIL 9 in prevention of certain HPV-related cancers and diseases later in life,” said Eliav Barr, PhD, senior vice president, head of global clinical development, and chief medical officer at Merck Research Laboratories, in a press release. “HPV-related cancers and diseases are a significant public health issue. These strong study results serve as a reminder that we need to do everything we can to expand and recover vaccination rates globally to help protect all eligible people from certain HPV-related cancers.”

The study showed a peak at month 7 of the antibody assessments that were calculated through geometric mean titers, with a decrease through 126 months. However, most of the individuals involved in the research stayed seropositive throughout the study.

The authors found that 99.6% to 100% of study participants were seropositive for the targeted HPV types at month 7, and 81.3% to 97.7% remained seropositive at month 126 depending on the HPV type. Based on the HPV-9 immunoglobulin G immunoassay, 94.9% to 100% of participants were seropositive at month 126.

Other results included a lack of findings of vaccine-target HPV type high-grade diseases in females— specifically cervical intraepithelial neoplasia,adenocarcinoma in-situ, vulval intraepithelial neoplasia, vaginal intraepithelial neoplasia, and certain cancers. Vaccine-targeted HPV type diseases were also not reported in males—specifically penile intraepithelial neoplasia and other certain cancers.

The LTFU study did not include any adverse effects of deaths with the use of Gardasil 9. Immediately following vaccination there is a risk of developing syncope, causing the individual to fall, although the patients are monitored for 15 minutes after the injection. The most common adverse reactions included pain and swelling in the injection site, as well as headache.

Reference:

Long-Term Follow-up Data on Sustained Immunogenicity and Safety for GARDASIL 9 Published in Pediatrics. Merck. News release. September 5, 2023. Accessed September 6, 2023. https://www.merck.com/news/long-term-follow-up-data-on-sustained-immunogenicity-and-safety-for-gardasil9-published-in-pediatrics/.