STORY-TRÅD·nyheter

HPV prevalence falls among young Brazilians after vaccination

The prevalence of the main types of HPV fell by nearly half in Brazil following vaccination, according to the largest study ever conducted in Latin America assessing the vaccine’s efficacy. Data collected in 2016 and 2017 show that 14.98 percent of participants had already been infected with at least one of the four types covered by the vaccine (6, 11, 16, and 18). In samples collected between 2020 and 2023, however, this proportion stood at 7.95 percent. Notícias relacionadas:COVID-19 still worrying five years after vaccination started in Brazil.Campaign to administer 89,000 vaccine doses in indigenous territories.Brazil: Four in ten cancer deaths preventable.The Pop-Brasil study was conducted by Moinhos de Vento Hospital in partnership with the Ministry of Health. In the first phase, samples from 6,388 unvaccinated participants of both sexes were analyzed. The second phase included more than 10,000 participants, both vaccinated and unvaccinated. Samples were collected at healthcare facilities. In both phases, the study focused on young people aged 16 to 25 years, according to Eliana Wendland, an epidemiologist and the study’s lead researcher: “This age group has the highest prevalence of HPV because it coincides with the onset of sexual activity. It was also selected because individuals in this group should already have been vaccinated.” Unfortunately, that was not the case. Among the girls and women included in the study, only 61.8 percent had been vaccinated, and the proportion was even lower among male participants, at 31.1 percent. The ideal vaccination coverage rate is 90 percent. Even so, the vaccine demonstrated its potential. Among the girls and women, the prevalence of HPV types covered by the vaccine was 15.6 percent in the first phase, when only unvaccinated individuals participated in the study. In the second phase, however, detection of these HPV types among vaccinated participants dropped to 3.1 percent. “Herd immunity” According to Wendland, the study also found evidence that the vaccine has already contributed to a “herd immunity” effect: “We also observed a population-wide effect of vaccination among the girls. Even among those who were not vaccinated, we observed a decrease in HPV prevalence.” This occurs because high vaccination coverage reduces the circulation of disease-causing agents, indirectly protecting the entire population. Among unvaccinated girls and women, the prevalence of the four HPV types targeted by the vaccine was 10.5 percent in the second phase of the study. Among men, the prevalence of the HPV types targeted by the vaccine fell from 13.8 percent to 4.6 percent among vaccinated participants, but there was no statistically significant change among unvaccinated participants in the second phase. According to Wendland, the explanation lies in the low vaccination coverage among this group. “This finding is not unexpected, since boys tend to receive less encouragement to get vaccinated against HPV than girls, in part because the virus is still widely perceived as primarily a cause of cervical cancer,” notes the preview of the article to be published in the journal npj Vaccines, which presents the study’s results. Effective vaccination Another piece of data underscoring the vaccine’s power and importance is that, between the two phases of the study, the overall prevalence of HPV in the population - considering all existing subtypes - rose from 46.7 percent to 56.6 percent, in contrast to what was observed for the four subtypes targeted by the vaccine. The study also found evidence that the current single-dose regimen offered by Brazil’s national public healthcare system, the SUS, is effective, as there was no difference in HPV prevalence among people vaccinated with one, two, or three doses. HPV vaccination through the SUS began in 2014, initially targeting only girls, but was expanded to include boys in 2017, with some changes to the eligible age range over the years. In 2024, the basic vaccination schedule changed from two doses to one. Today, the target population includes all children and adolescents aged 9 to 14 years, as well as certain vulnerable adult groups, such as immunocompromised individuals, victims of sexual violence, users of pre-exposure prophylaxis for HPV prevention, and people with a previous history of precancerous cervical lesions. HPV, short for human papillomavirus, is the leading cause of cervical cancer, but it can also cause cancers in other organs, such as the penis, anus, and throat. Not all HPV subtypes are carcinogenic, but the vaccine available through Brazil’s public health system protects against the four main oncogenic HPV types.