The HPV vaccine appears to be working. Countries with vaccination programmes are lowering the rate of virus infection, precancerous lesions and genital warts in girls and women. Boys and men are benefiting too, even when they are not vaccinated.
That’s the conclusion of a review of 65 studies across 14 high-income countries, including 60 million people, over 8 years. “Our results provide strong evidence that HPV vaccination works to prevent cervical cancer in real-world settings,” says Mélanie Drolet of Laval University in Quebec, who led the work.
HPV vaccination programmes are currently running in around 115 countries, says Marc Brisson, also at Laval University in Quebec, who co-authored the study. It is too soon to measure how these programmes might impact rates of cervical cancer, so the team looked at rates of HPV infection and the incidence of precancerous lesions and anal and genital warts, which can result from infection.
The team found that, between 5 and 8 years into a vaccination programme, the prevalence of two strains of HPV that the vaccine protects against dropped by 83 per cent among teenage girls and 66 per cent in women aged 20 to 24. The prevalence of the virus also dropped by 37 per cent in women aged between 25 and 29, even though most were unvaccinated.
The incidence of anogenital warts also dropped – by 67 per cent among girls aged 15 to 19, and 54 per cent in women aged 20 to 24. Diagnoses of anogenital warts was reduced in unvaccinated boys and men too – by 48 per cent in boys aged 15 to 19, and 32 per cent in men aged 20 to 24. This suggests that vaccinating girls and young women can protect boys and men too, thanks to herd immunity, says Brisson.
The team also looked at the incidence of precancerous lesions in girls and women. Cervical intraepithelial neoplasia (CIN) is the term given to abnormal cervical cells, which can be diagnosed as CIN1, CIN2 or CIN3. The latter two can develop into cervical cancer if untreated.
Diagnoses of CIN2 and CIN3 decreased by 51 per cent among 15 to 19-year-old girls between 5 and 9 years into vaccination programmes. Incidence of these lesions in unvaccinated women, on the other hand, increased over the same period.
There is some variation between countries. Some use HPV vaccines that offer protection against more strains of the virus, for example. And while some countries offer vaccination only to teenage girls, others include boys and young women and men. Those that provided wider virus protection to more people saw the fastest and greatest impacts.
Around 80 per cent of high-income countries currently have vaccination programmes, but only around 20 per cent of middle- and low-income countries do, says Brisson. “Vaccinating girls in these countries would have the greatest impact on the worldwide burden of HPV-related cancer,” he says.
Journal reference: The Lancet, DOI: 10.1016/S0140-6736(19)30298-3
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