Vaccination against HPV drastically reduces the risk of cervical cancer

A Swedish study reports that young girls who receive the human papillomavirus vaccine before the age of 17 have a 90% lower risk of developing invasive cervical cancer.

Cervical cancer is unique in that it is cancer of viral origin, caused by a class of viruses called human papillomavirus (HPV). Most HPV infections start soon after having sex for the first time and are usually more common as the number of sexual partners increases.

In most cases, the immune system is able to neutralize these viruses and prevent the development of cancer.

On the other hand, when they manage to establish themselves in the cells of the cervix, HPVs produce proteins that abolish the function of important tumor suppressors (p53 and Rb) and thus promote the uncontrolled growth of these cells. .

Block cancer

The arrival on the market, fifteen years ago, of vaccines capable of neutralizing HPVs completely revolutionized the way we fight cervical cancer.

Whereas previously the only available approach against this cancer was to diagnose it as early as possible (using Pap smears), these vaccines now help prevent cancer at the source, by preventing viruses from infecting them. cells of the cervix.

So far, the efficacy of these vaccines has mainly been evaluated for their ability to reduce two key stages in the development of cervical cancer, namely infection of cervical cells by viruses and the onset of cervical cancer. grade 2 cervical intraepithelial neoplasia (CIN-2 +), i.e. precancerous lesions at a very high risk of progressing to cancer.

The results obtained are very encouraging: an analysis of the results of some forty studies (comprising in total more than 60 million individuals) revealed that 5-8 years after vaccination, the prevalence of HPV infections has decreased. 83% among girls aged 13-19 and 66% among those aged 20-24 1.

More importantly, the vaccination caused a marked decrease (51%) in the incidence of precancerous CIN2 + lesions in young women aged 15-19 and by 31% in those aged 20-24.

The potential for preventing cervical cancer with these vaccines is therefore enormous.

Cancer vaccines

The development of invasive cervical cancer is a relatively slow process, with a latency of 5 to 20 years (and sometimes longer) between the acquisition of a persistent HPV infection and the development of cancer. invasive 2.

Since the first large-scale vaccination campaigns began in several countries around 2007, we are therefore beginning to be able to directly assess the impact of these vaccines on the incidence of cervical cancer.

A first direct evaluation of this preventive potential has just been reported in the prestigious New England Journal of Medicine 3.

The study involved 1,672,983 Swedish girls and women aged 10 to 30, of whom 527,871 had received an HPV vaccine during the study period (2006-2017).

The researchers observed that the incidence of cervical cancer dropped drastically with vaccination, from 5.2 cases per 100,000 in unvaccinated women to 0.7 cases per 100,000 vaccinated women.

The protective effect of the vaccine is particularly pronounced when vaccination is performed before the age of 17, with a 90% decrease in the incidence of cancer.

These data therefore confirm that the vaccine is optimal at a young age, ideally before the start of sexual relations and young girls’ exposure to the virus.

Drolet M et al. Population-level impact and herd effects following the introduction of human papillomavirus vaccination programs: updated systematic review and meta-analysis. Lancet 2019; 394: 497-509.

Schiffman M et al. Human papillomavirus and cervical cancer. Lancet 2007; 370: 890-907.

Lei J et al. HPV vaccination and the risk of invasive cervical cancer. N. Engl. J. Med. 2020; 383: 1340-1348.

www.journaldequebec.com

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