Most of the types of human papillomavirus (HPV) that cause oral and other cancers can be eliminated if both girls and boys are vaccinated, according to researchers at the Karolinska Institutet in Sweden. Both genders will be offered vaccination in Sweden as of 2020.
The researchers began a randomized study in 2007 inviting 80,000 young people between the ages of 12 and 15 from 250 schools in 33 towns to take part. In 11 towns, both boys and girls received HPV vaccination. In another 11, only girls were vaccinated. In the remaining 11, the participants were vaccinated against a totally different virus as a control.
General HPV screening at the age of 19 showed that the vaccination of both genders prevented HPV infections in society much more effectively than vaccinating girls only. A gender-neutral strategy also was effective at preventing HPV infections in unvaccinated girls.
HPV was included in the Swedish vaccination program in 2012. To date, the vaccine has only been offered to girls. In 2019, though, the government decided to offer it to both genders as of autumn 2020.
“Our study is unique because the entire population of the communities included in the study was invited to take part, and the choice of vaccination strategy was randomized by community,” said study leader Matti Lehtinen of the Department of Laboratory Medicine.
“The results have definitely influenced the decision about offering HPV vaccination to boys, which more and more countries are also deciding,” said Lehtinen.
Mathematical modeling was used to calculate what the results of the randomized HPV vaccination study would mean for programs with different vaccination coverage. The improved effectiveness of vaccinating both boys and girls is particularly important if only 80% or fewer of girls are vaccinated.
“If only girls are offered HPV vaccination, not even a school-based vaccination program will be able to eliminate the most oncogenic HPV, type 16, ever,” said Simopekka Vänskä, docent at the Finnish Institute for Health and Welfare and the study’s first author.
“Vaccination of both boys and girls with a 75% participation rate can, however, eliminate HPV-16 even in people under 30, which is the segment of the population that is mainly spreading the infection. The elimination will take place only in a few years after the vaccinated cohorts achieve these ages,” Vänskä said.
The World Health Organization has established the elimination of cervical cancer as a priority objective.
“The results of the randomized study of different vaccination strategies now published gives us information about how this objective could be achieved at the earliest possible time,” said Lehtinen.
HPV causes a variety of cancers, predominantly cervical cancer in women and cancer of the oropharynx in women and men. Almost everyone has had at least one sexually transmitted HPV infection in his or her life, the researchers report.