Cervical cancer rates are 87 per cent lower in women vaccinated against human papillomavirus (HPV) when they were between the ages of 12-13 than in previous generations, confirms a new study published in The Lancet.
The researchers also found reductions in cervical cancer rates of 62 per cent in women offered vaccination between the ages of 14-16, and 34 per cent in women aged 16-18. This is the first direct evidence of the prevention of cervical cancer using the bivalent vaccine, Cervarix.
HPV vaccination has been introduced in 100 countries as part of efforts by the World Health Organization (WHO) to eliminate cervical cancer. England initially used a bivalent vaccine that protects against the two most common types of HPV responsible for approximately 70-80 per cent of all cervical cancers. The English HPV vaccination programme was introduced in 2008, with vaccines given to women between 12-13 years old and “catch-up” vaccinations offered to older age groups, up to 18.
“Although previous studies have shown the usefulness of HPV vaccination in preventing HPV infection in England, direct evidence on cervical cancer prevention was limited,” says professor Peter Sasieni, King’s College London, one of the authors of the paper.
“Early modelling studies suggested that the impact of the vaccination programme on cervical cancer rates would be substantial in women aged 20-29 by the end of 2019. Our new study aims to quantify this early impact. The observed impact is even greater than the models predicted,” said Sasieni.
The study looked at population-based cancer registry data between January 2006 and June 2019 for seven cohorts of women who were aged between 20 and 64 at the end of 2019. Three of these cohorts formed the vaccinated population, where women were vaccinated with Cervarix between the ages of 12-13, 14-16 and 16-18. Incidences of cervical cancer and non-invasive cervical carcinoma (CIN3) in the seven populations were recorded separately.
During the study period, 28,000 diagnoses of cervical cancer and 300,000 diagnoses of CIN3 were recorded in England. In the three vaccinated cohorts, there were around 450 fewer cases of cervical cancers and 17,200 fewer cases of CIN3 than expected in a non-vaccinated population. The research found reductions in cervical cancer rates of 87 per cent (with a confidence interval of 72-94 per cent) in women targeted between the ages of 12-13 (89 per cent of whom received at least one dose of the HPV vaccine and 85 per cent of whom had received three jabs and were fully vaccinated), 62 per cent (CI: 52-71%) in women potentially vaccinated between the ages of 14-16, and 34 per cent (CI: 25-41%) in those eligible for vaccination between the ages of 16-18 (60 per cent of whom received at least one dose and 45 per cent of whom were fully vaccinated). The corresponding reductions in CIN3 rates were 97 per cent in women vaccinated between the ages of 12-13, 75 per cent in women vaccinated between the ages of 14-16 and 39 per cent in women vaccinated between the ages of 16-18.
“This study provides the first direct evidence of the impact of the UK HPV vaccination campaign on cervical cancer incidence, showing a large reduction in cervical cancer rates in vaccinated cohorts. As expected, vaccination against HPV was most effective in the cohorts vaccinated at ages 12-13 amongst whom the uptake was greatest and prior infection least likely,” says Dr Kate Soldan from the UK Health Security Agency and co-author.
“This represents an important step forwards in cervical cancer prevention. We hope that these new results encourage uptake as the success of the vaccination programme relies not only on the efficacy of the vaccine but also the proportion of the population vaccinated,” added Dr Soldan.
Lucy Elliss-Brookes, associate director for Data Curation at NHS Digital and one of the authors of the paper, said: “The findings of this study are hugely important in encouraging those eligible to take up the vaccine, but also in demonstrating the power of data in helping medical researchers and the NHS to understand what causes cancer and how best to diagnose, prevent and treat it.”
The authors acknowledge some limitations with the study, principally that cervical cancer diagnosis is rare in young women. In addition, the number of registered cases of cervical cancer is impacted by the age at which women are screened; most of the follow-up for women in vaccinated cohorts occurred under the age of 25 and small differences in the age of first screening can have a large impact on registered cervical cancer cases in women below this age. Because the vaccinated populations are still young, the authors stress that this means that it is still too early to assess the full impact of HPV immunisation on cervical cancer rates. However, it is important to note that the two most common HPV infections which the bivalent vaccine protects against are present in as many as 92 per cent of women diagnosed with cervical cancer before the age of 30.
It should also be noted that the bivalent vaccine Cervarix was used in the UK from 2008-2012. Since September 2012, the quadrivalent vaccine Gardasil has been used instead.