THE INCIDENCE of cervical cancer is reduced by 87% in women vaccinated against human papillomavirus (HPV) between 12 and 13 years, by 62% in those vaccinated between 14 and 16 years and by 34% in those reached between 16 and 18. These are the data of a study by King’s College London funded by Cancer Research UK and published in the Lancet. As well as the first direct evidence – underline the authors – of the impact of the bivalent anti-HPV vaccine on the population, which protects against strains 16 and 18: the most common and believed to be responsible for about 70-80% of all cervical cancers uterine and 70% of HPV-related precancerous lesions of the vulva and vagina, as well as 90% of anal cancers.
Better than expected
In Great Britain the vaccination program against the HPV virus was introduced in 2008, with bivalent vaccination for adolescents between 12-13 years and so-called “recovery” inoculations – that is offered to older girls – up to 18 years. . “The usefulness of vaccination in preventing HPV infection has been demonstrated in England by previous studies, but direct evidence of cervical cancer prevention was limited,” said Peter Sasieni of King’s College London and one of the authors of the research: “The first modeling studies – added Sasieni – suggested that the impact of the vaccination program on cervical cancer would manifest itself in an appreciable way in women aged 20-29 at the end of 2019. The goal of our study was to quantify this impact, which was even greater than that predicted by the models “.
Seven cohorts
The researchers looked at data collected by the Cancer Registry between January 2006 and June 2019 from seven cohorts of women who were between 20 and 64 years old at the end of 2019. The vaccinated population consisted of three cohorts: women vaccinated with the bivalent vaccine at 12-13 years, those who had received it at 14-16 years and those who had been tested at 16-18 years. In addition to the impact of vaccination on the number of cervical cancer cases, the impact of CIN3, an acronym that stands for cervical intraepithelial neoplasia, was also evaluated: a tumor in which the altered cervical cells do not go beyond the epithelium but may evolve over time.
The results
During the study period, 28,000 diagnoses of cervical cancer and 300,000 of CIN3 were recorded in England. And here is the important fact: in the three vaccinated cohorts there were about 450 fewer cases of cervical cancer and 17,200 of CIN3 than expected in the unvaccinated population. Hence the calculations that lead to cervical cancer reductions of up to 87% in those who had been vaccinated between 12 and 13 years. As for the cases of CIN3, the reduction was 97% in vaccinated women between 12 and 13 years, 75% in those vaccinated between 14 and 16 years and 39% in vaccinated women between 16 and 18 years.
Encourage vaccination (and understand the power of data)
“As we expected, HPV vaccination was most effective in cohorts of girls who were vaccinated at the age of 12-13, among whom a pre-immunization infection is less likely,” said Kate Soldan of ‘United Kingdom health safety agency and co-author of the Lancet study. but also the percentage of the population that gets vaccinated. “” The results of this study are extremely important to encourage those who are eligible to get vaccinated, but also to show the great power that data have in helping researchers and the NHS to understand what causes cancer and how best to diagnose, prevent and treat it, ”added Lucy Elliss-Brookes, associate director of NHS Digital’s Data Curation Service, an that you are among the authors of the research.
The limits of the study
The study has some limitations. For example the question of the age of vaccinated women; who are still too young to assess the full impact of immunization on cervical cancer rates. But it is also important to note that the two most common HPV infections, against which the bivalent vaccine protects, are present in 92% of women diagnosed with cervical cancer before age 30. It should also be noted that the bivalent vaccine has been used in the UK from 2008-2012, and that another quadrivalent vaccine has been used since September 2012, which also protects against strains 6 and 11, responsible for 90% of genital warts.
The message for low-income countries
“The extent of the HPV vaccination effect documented by this study is expected to spur vaccination programs in low- and middle-income countries, where cervical cancer is a far greater public health problem than in other countries. countries with established vaccination and screening systems – Maggie Cruickshank of the University of Aberdeen wrote in a study commentary: increased immunization rate is a key element of success ”.
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