Research published in Cell Host & Microbe in November 2023 reaches a “somewhat provocative conclusion” that HPV vaccination is so effective that screening protocols might need a review. The paper suggests that “comprehensive human papillomavirus (HPV) vaccine implementation” is “essentially changing the ecological conditions of this virus-host interaction worldwide”. The researchers included over 60,000 women from 33 Finnish communities born between 1992 and 1994. They were divided randomly into groups based on their cities’ HPV vaccination strategies and followed up after vaccination to test for 16 types of genital HPV. 

HPV and vaccine strategies 

HPV is described by the CDC as the “most common STI”. Although common, we do have effective vaccines to prevent the diseases caused by HPV, which include some types of cancer. This vaccine is currently recommended for “everyone” up to the age of 26 in the US. In the UK the recommended group includes other people at “higher risk”.  Although we have this effective vaccine, the latest research aims to evaluate several different immunisation strategies and understand the effects of a successful strategy. 

What does the study find? 

The study evaluates the long-term, population level effect of “community-randomised gender-neutral and girls-only HPV vaccination” on the “ecology” of the remaining oncogenic HPVs among young adult women who were vaccinated in adolescence. The researchers identified a “significant depletion” of high-oncogenicity vaccine-targeted HPV types 16,18,31, and 45 in gender-neutral and girls-only vaccination communities at the 4-year follow up after vaccination. However, this was consistent 8 years after vaccination “only among gender-neutral vaccination communities”.  

Their “most important finding” is the “significantly increased” oncogenic HPVs ecological diversity from 4 to 8 years after vaccination “exclusively in gender-neutral vaccination communities”, despite the clearance of the vaccine-targeted types in these communities”. 

“This rising ecological diversity of the oncogenic HPVs in gender-neutral vaccination communities with a stronger herd immunity compared with girls-only vaccination communities is likely the first recorded sign of ecological niche occupation by the non-vaccine-targeted HPV post-population-level vaccination.”  

So, what does this all mean? Previous research has demonstrated the “need to opt for gender-neutral HPV vaccination strategies” to meet WHO-targeted eradication of the oncogenic HPVs. To do this, the authors claim that we must “understand the evolutionary dynamics of these oncoviruses”, particularly under “long-term vaccine-induced selective pressure”.  

“Taken together, understanding the differences in the transmissibility, antigenic variation, and oncogenic potential of the remaining HPV types in the newly established ecological niche following different vaccination strategies creates new basis for future cancer screening of HPV-vaccines and the herd effect protected non-HPV-vaccinated women and men.”  
Painting a picture 

Professor Ville Pimenoff, lead author, senior researcher at Karolinska Institutet, and professor at the University of Oulu, told STAT that it is “clear that there’s a stronger protection” achieved when you “have both genders vaccinated”. 

“This paper nicely paints a picture that indeed the vaccine is most efficient when you vaccinate boys and girls.”  

Professor Pimenoff highlights that “apart from the individual” protection, you also secure “herd protection”. The findings, he suggests, might indicate a need to rethink screening approaches. There is a cohort of women about to reach screening age in Finland who have been vaccinated. Different HPV varieties may be detected, leading to a “reasonable number of women” testing positive for types that are included in protocols but are “low risk”.  For these people, there is a chance of “overdiagnosis” or misdirection of public health resources. Therefore, Professor Pimenoff believes that screening could be limited to high-oncogenic types and conducted less frequently.

Others weigh in 

Professor Stephen Duffy of Queen Mary University of London is quoted by Science Media Centre, praising the “interesting and well conducted study”. However, he urges interpretive caution. 

“While we should not rush to change screening policy…it would be prudent to check if these results are replicated elsewhere, and to consider the implications for which populations we screen and how we screen them.” 

Professor Margaret Stanley of University of Cambridge warned that, despite the “high standard” of the analyses, we should not rush to change the HPV screening programme in the UK. 

“Evidence from national immunisation programmes with high coverage and good surveillance of HPV infection and disease pre- and post-vaccination is needed before re-evaluation of screening programmes and strategies.”  

How do you think this study could inform national screening? If you are interested in more insights into the latest vaccine research don’t forget to join our newsletter list here.