Primary prevention of cervical cancer with vaccination is critical in any cancer prevention program
Benard VB, Castle PE, Jenison SA, et al; New Mexico HPV Pap Registry Steering Committee. Population-based incidence rates of cervical intraepithelial neoplasia in the human papillomavirus vaccine era. JAMA Oncol. 2017;3(6):833-837.
Luostarinen T, Apter D, Dillner J, et al. Vaccination protects against invasive HPV-associated cancers. Int J Cancer. 2018;142(10):2186-2187.
The success story of HPV vaccination, after more than a decade of use, continued to unfold in important ways over the past year.
Safety. With tens of millions of doses delivered, we know that the vaccine is safe, and we have retreated on some of the precautions that we once took: For example, we no longer perform a routine pregnancy test before vaccination on reproductive-age women.
Efficacy. We have learned, based on what we see in Australia and Western Europe, that vaccination is highly effective. We are also starting to see evidence of efficacy in areas of the United States, even though the vaccine is voluntary and there are no school-based recommendations. And we know that herd vaccination is very effective. The 2 studies described here add to our understanding of how vaccination is having an impact on endpoints.
Findings of the 2 studies
HPV vaccination has a direct impact on the precursor of cancer, CIN. Benard and colleagues examined data from the New Mexico HPV Pap Registry, a mandatory statewide surveillance system of cervical cancer screening that captured estimates of both screening prevalence and CIN since the time HPV vaccination was introduced in 2007 to 2014. The investigators examined registry data to gauge trends in the rate of CIN and to estimate the effect of HPV vaccination on that rate when adjusted for changes in screening for cervical cancer.
The incidence of CIN declined significantly across all grades in 2 groups between 2007 and 2015: females aged 15 to 19 years and females aged 20 to 24 years (but not in females 25 to 29 years of age). During those years, mean uptake of HPV vaccination among females 13 to 17 years of age reached as high as 40% (in 2014).
Although a reduction in CIN2 and CIN3 precancers "are early benchmarks for achieving this aim [of reducing the rate of cancer]," the investigators note, a reduction in CIN1 is "a direct measure of reductions in HPV infections requisite to the development of almost all invasive cervical cancer."
Benard moves on to conclude that a reduction in clinical outcomes of CIN among groups who are partially vaccinated for HPV is going to change clinical practice and reduce the cost-effectiveness of clinical care that supports prevention of cervical cancer. Of greatest importance, modalities and strategies for screening, and management algorithms, are going to need to evolve as HPV vaccination and cervical screening are integrated in a rational manner. Furthermore, it might be feasible to factor in population-level decreases in CIN among cohorts who are partially vaccinated for HPV when reassessing clinical practice guidelines for cervical cancer screening.
What does this mean? As we start to eliminate HPV from the population, any positive screening result will be that much more meaningful because the outcome--cervical cancer--will be much rarer. The onus will be on providers and public health officials to re-strategize how to screen what is going to be a widely-vaccinated population; more and more, we will be looking for needles in a haystack.
How are we going to someday screen women in their 20s who were vaccinated at 11 or 12 years of age? Likely, screening will start at a later age, and screening will be conducted at longer intervals. Any finding of HPV or disease is going to be highly significant, and likely, far less frequent.
HPV vaccination protects against invasive HPV-associated cancer. Luostarinen and colleagues report proof of highly efficacious protection offered by a population-based HPV vaccination program in Finland, in the form of a decrease in the key endpoint: cases of invasive HPV-associated cancer. Examining vaccinated (3,331 females) and unvaccinated (15,665 females) cohorts in the nationwide Finnish Cancer Registry, the investigators identified 10 cases of HPV-caused cancer (8 cervical, 1 oropharyngeal, 1 vulvar) in the unvaccinated females and 0 cases in vaccinated females--a statistically significant difference.
From the evidence gathered in this first intention-to-treat trial, the investigators conclude that vaccination protects against invasive HPV-associated cancer--what they call "an awaited, pivotal corollary" to high vaccine efficacy against HPV infection.
Summing up
This success story continues to unfold, despite well-organized, antivaccine campaigns. The HPV vaccine has been an easy target: It is novel, it involves a sexually transmitted infection, and the endpoint of protecting against invasive HPV-associated cancer is years--decades--away. But antivaccine groups can no longer argue the point that studies have not been designed to yield evidence of the impact of the vaccine on decisive endpoints, including cervical cancer.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
The exciting news that the sought-out endpoint of HPV vaccination -- prevention of invasive HPV-associated cervical cancer -- is being realized. This should all the more energize you to:
- urge vaccination for your patients in whom it is indicated
- emphasize vaccine coverage in the young -- especially for the routinely recommended age group of 11 - and 12-year-olds
- strenuously reject and counter arguments made by segments of the public that HPV vaccination is neither safe nor necessary
- prepare for potential changes down the road in practice guidelines regarding screening (eg, raising the age at which screening begins) as the impact of vaccination on the health of women is felt.
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