HPV vaccination provides “sustained protection” against cervical cancer

(Press-News.org) Human papillomavirus (HPV) vaccination is associated with a significantly reduced risk of invasive cervical cancer, with no indication of waning protection up to 18 years after vaccination, finds a study from Sweden published by The BMJ today.

HPV is one of the most common sexually transmitted infections and many countries offer vaccination to protect girls against cervical cancer, and other related cancers, in later life.

But evidence on the long term durability of vaccine protection against HPV-related diseases is scarce, and it is also unclear how waning immunity, if present, may differ by age at vaccination.

To address these knowledge gaps, researchers in Sweden used nationwide registers to evaluate the risk of invasive cervical cancer after receiving the quadrivalent HPV vaccine over an 18-year follow-up period (1 January 2006 to 31 December 2023).

They also examined risk reduction by time since vaccination and population-level changes in invasive cervical cancer cases since the introduction of HPV vaccination programmes in Sweden.

Their findings are based on 926,362 girls and women living in Sweden between 2006 and 2023 who were born between 1985 and 2001 with no previous HPV vaccination or diagnosis of invasive cervical cancer at the start of follow-up in 2006.

Participants were followed up to a maximum age of 38 years, with those vaccinated before age 17 followed up to a maximum age of 34.

A range of potentially influential factors were accounted for in the analysis including age, county of residence, mother’s country of birth and history of high-grade cervical lesions and non-cervical cancers, parental education and income.

During follow-up, 365,502 (40%) participants received at least one dose of the quadrivalent HPV vaccine and 930 cases of invasive cervical cancer were identified (97 in vaccinated and 833 in unvaccinated individuals).

Individuals vaccinated before age 17 had a substantially (79%) lower risk of cervical cancer compared with the unvaccinated group, with sustained protection (77% lower risk) for 13-15 years after vaccination.

Individuals vaccinated at age 17 or older had a 37% lower risk of invasive cervical cancer compared with the unvaccinated group, with a 46% lower risk 10-12 years after vaccination and a 77% lower risk 13-15 years after vaccination.

The results also show a population level decline in cervical cancer cases over time.

The rate of invasive cervical cancer was highest in women born between 1985 and 1988, reaching around 250 cases per 100,000 by age 38. This rate progressively decreased for women born in 1989-1992 and 1993-1998 and was significantly lower for women born between 1999 and 2001 at 4 per 100,000 by age 24.

These are observational findings and authors acknowledge that some vaccinated women may have been misclassified as unvaccinated. Nor can they rule out a healthy volunteer bias or the possibility that other unmeasured factors, such as smoking and sexual activity, may have affected their results.

However, this large study based on high-quality, nationwide data allowed them to examine the risk of invasive cervical cancer across multiple time intervals since vaccination, and results were consistent after further analyses, suggesting they are robust.

As such, they conclude: “This study provides evidence of sustained protection against invasive cervical cancer throughout 18 years of follow-up, with no indication of waning protection. These findings further support global strategies for eliminating cervical cancer as a public health problem by achieving high-coverage of routine HPV vaccination.”

As such, they say: “We found sustained risk reduction of invasive cervical cancer after quadrivalent HPV vaccine. No indication of waning protection was observed among the vaccinated population.”

“These findings further support global strategies aimed at cervical cancer elimination through high vaccine coverage, particularly in younger populations, and emphasise the critical role of routine immunisation programmes,” they add.

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