HPV vaccine helps to significantly reduce rate of cervical cancer infections and pre-cancerous lesions, WHO study finds
HPV infections declined substantially since a vaccine was introduced, a global study has found. The global study provides 'strong evidence' the HPV vaccine prevents cervical cancer.
Cervical cancer - the fourth most frequent cancer in women with an estimated 570,000 new cases in 2018 - is caused by the human papillomavirus (HPV). Strong evidence now shows that the HPV vaccine has substantially reduced the number of infections as well as the pre-cancerous cervical lesions caused by the virus, making it possible to eliminate cervical cancer in the coming decades. The results of the World Health Organization-funded study, published in The Lancet, show that HPV infections dropped by 83% among girls aged 13 to 19 and 66% among women aged 20 to 24.
“HPV vaccination is still too recent to directly measure its effects on cervical cancer as it can take decades to develop. However, our analyses show that vaccination is producing substantial reductions in the infections that cause cervical cancer and pre-cancerous lesions. These reductions are a first sign that vaccination could eventually lead to the elimination of cervical cancer as a public health problem. We are now trying to determine when elimination could be achieved and which vaccination and screening programs could help us achieve it faster,” states lead author Mélanie Drolet.
According to the World Health Organization (WHO), HPV is a group of viruses that are extremely common worldwide. There are over 100 types of HPV, of which at least 14 are cancer-causing. Further, two types of HPV (16 and 18) cause 70% of cervical cancers and pre-cancerous cervical lesions. Infections caused by HPV are among the most common sexually transmitted diseases. Certain forms of the virus can lead to anogenital warts, while others cause lesions that can develop into cancer of the mouth, throat, vagina, vulva, anus, or penis, and particularly the cervix. “HPV is found in almost 100% of cervical cancer cases,” says Drolet.
In 2018, approximately 311,000 women died from cervical cancer. According to the WHO, a comprehensive cervical cancer control includes primary prevention (vaccination against HPV), secondary prevention (screening and treatment of pre-cancerous lesions), tertiary prevention (diagnosis and treatment of invasive cervical cancer) and palliative care.
Since 2007, 99 countries and territories have introduced HPV vaccination programs. For the present study, the research team headed by Université Laval’s Faculty of Medicine Professor Marc Brisson, conducted a meta-analysis of 65 studies in 14 high-income countries that have set up HPV vaccine programs in the last ten years. With data on 60 million people and up to 8 years of post-vaccination follow-up, the researchers compared the frequency of HPV infections, anogenital warts, and pre-cancerous cervical lesions before and after the programs were launched.
“Our results show compelling evidence of the substantial impact of HPV vaccination programs on HPV infections and CIN2+ (pre-cancerous cervical lesions) among girls and women, and on anogenital warts diagnoses among girls, women, boys, and men. After 5 to 8 years of vaccination, the prevalence of HPV 16 and 18 decreased significantly by 83% among girls aged 13–19 years and decreased significantly by 66% among women aged 20–24 years. The prevalence of HPV 31, 33, and 45 decreased significantly by 54% among girls aged 13–19 years,” says the paper.
After 5–9 years of vaccination, pre-cancerous cervical lesions decreased significantly by 51% among screened girls aged 15–19 years, and it dropped by 31% among women aged 20–24 years.
Results further reveal that after five to eight years of vaccination, anogenital wart diagnoses decreased significantly by 67% among girls aged 15–19 years, it went down substantially by 54% among women aged 20–24 years, and by 31% for women aged 25–29 years. “Among boys aged 15–19 years anogenital wart diagnoses decreased significantly by 48% and among men aged 20–24 years they decreased significantly by 32%,” say the findings.
“Our results provide strong evidence of HPV vaccination working to prevent cervical cancer in real-world settings, as both the cause (high-risk HPV infection) and proximal disease endpoint (CIN2+) are significantly declining. In terms of global policy implications, these results reinforce the recently revised position of WHO recommending HPV vaccination of multiple age cohorts of girls, and provide promising early signs that the WHO call for action on cervical cancer elimination might be possible if sufficient population-level vaccination coverage can be reached,” says the research team in the paper.