Researchers evaluated the immunogenicity, efficacy and safety of the human papillomavirus (HPV) vaccine in a group ten years after the last dose. Coordinated by Fiocruz Bahia researcher Edson Duarte Moreira Júnior and published in the journal Pediatrics, of the American Association of Pediatrics, the study followed 301 boys and 971 girls who received three doses of the 9vHPV vaccine in the baseline study (day 1, months 2 and 6) and enrolled in the extension.
The immunogenicity of a vaccine is related to its ability to stimulate the immune system to produce antibodies. Efficacy, in turn, refers to the ability of the immunizer to provide immunological protection against a given agent. Safety, on the other hand, is linked to the reporting of adverse events following immunization (AEFIs), and the study included the reporting of all serious adverse events (SAEs), deaths related to the vaccine, as well as pregnancies, which were followed up until the endpoint.
Long-term follow-up was carried out from August 27, 2009 (the participant's first visit in the baseline study) until April 22, 2021 (last visit). The monitoring was carried out at 40 sites in 13 countries (Belgium, Brazil, Colombia, Costa Rica, Peru, Poland, South Africa, South Korea, Spain, Sweden, Taiwan, Thailand, and the United States). Serum was collected until month 126, about 10 years and six months, for antibody evaluations by competitive Luminex immunoassay and immunoglobulin G-Luminex immunoassay. To analyze the efficacy in participants aged 16 and over, genital swabs were taken (to assess HPV DNA by polymerase chain reaction) and external genital examinations were carried out every six months.
The antibodies reached the peak of protection at around seven months, decreased more sharply between months seven and 12, and then gradually decreased thereafter until month 126. It was observed that antibodies peaked higher in participants aged between 9 and 12 than between 13 and 15. No serious adverse events were reported in the participants.
There were no cases of high-grade cervical, vulvar or vaginal intraepithelial neoplasia in female participants, of high-grade penile, perineal or perianal intraepithelial neoplasia in male participants, or genital warts in all participants, related to the HPV types targeted by the vaccine by the end of the follow-up. There was one case of low-grade neoplasia, probably caused by HPV type 39 and/or HPV type 59, given the detection of persistent infection with these types, not being considered a novel case as these two types are not covered by the 9vHPV vaccine.
The research concludes that the immunogenicity, efficacy and safety have been demonstrated over ten years after vaccination. The rates of persistent infection and disease related to the HPV types targeted by the vaccine are within the expected ranges, compared to the group of vaccinated people of a similar age in previous studies on the HPV vaccine efficacy.