Evidence of cancer-causing HPV types replacement by low cancer risk HPVs years after HPV vaccination of boys and girls revealed by a large community-randomized cohort study from Finland

Researchers from Universities of Oulu and Tampere, in collaboration with Karolinska Institutet, demonstrate for the first time that human papillomavirus (HPV) type replacement occurs: as HPV vaccination reduces the number of carcinogenic HPV types in a population, previously rare, less harmful HPV types appear to occupy this ecological niche. This drastic change in HPV type distribution eight years after gender-neutral vaccination which includes significant herd protection calls to rethink current cervical cancer screening approaches among vaccinated populations.

These novel findings published in the high-profile journal Cell Host & Microbe confirm that HPV vaccination is an effective way to protect the population from HPV-related cancers, especially when both girls and boys are vaccinated.

Moreover, the same study also refutes the previous epidemiological assumption that there is no type replacement among cancer-causing HPVs after vaccination. HPV type replacement refers to a situation where the viral types (ie. strains) targeted by the vaccine are lost as a result of vaccination, but are eventually replaced in the long run by less dangerous HPV strains in the population.

"The phenomenon stems from the human-viral interaction in which the HPV vaccination clears the cancer-causing viral types that are also typically most prevalent in the young population. This cleared viral ecological niche in a community is filled in subsequent years through selection with less harmful HPV types that are not targeted by the vaccine. Important here, however, is that these vaccine-untargeted HPV type infections are known to have low or no risk to progress into cancer,” says principal investigator Ville Pimenoff from the University of Oulu.

The study provides evidence that HPV vaccination radically changes the dynamics of cancer-related papillomavirus types in vaccinated populations. Most importantly, this newly emerging distribution of low cancer risk HPVs calls to redesign or stop current cervical cancer screening protocols in HPV vaccinated communities.

"Based on our results, it is clear that screening for cervical cancer and its precursors caused by HPV infection needs to change after large-scale vaccination," Pimenoff stresses. "For those who are vaccinated, it would be worth considering either less frequent screening or no screening at all. The results suggest that low-risk HPVs infections are increasing, but in practice these cases do not increase an individual's risk of cancer associated with HPV infection. Our currently unpublished follow-up study already gives clear indications of this as well."

This study led by Dr. Pimenoff is based on world’s largest community-randomized vaccination trial in which more than 30 000 Finnish girls and boys received a bivalent HPV vaccine between 2007 and 2008. Long-term follow-up of the study has been carried out in 33 different cities in Finland for more than 16 years.

The HPV vaccination is part of Finland's national vaccination programme. The vaccine provides protection against cervical cancer, but also against other HPV-induced anogenital, oral and neck cancers.

The research has been funded by the Jane and Aatos Erkko Foundation, the Sigrid Jusélius Foundation, the Finnish and Swedish Cancer Foundations, the Academy of Finland, Karolinska Institutet Foundation and the EU's Horizon 2020 programme, among others.

Research article: Pimenoff VN. et al. Ecological diversity profiles of non-vaccine-targeted HPVs after gender-based community vaccination efforts. Cell Host & Microbe 31 (2023) pp. 1921-1929.

Link to the article

Last updated: 8.11.2023