乌鸦传媒

The introduction of a human papillomavirus (HPV) immunization program in England substantially reduced cases of cervical cancer and incidence of grade 3 cervical intraepithelial neoplasia (CIN3) in young women, particularly those who received the vaccine at the age of 12 or 13, researchers found.

In their register-based population study, estimated relative reductions in cervical cancer rates were 87% for those offered vaccination at ages 12 to 13, 62% at ages 14 to 16, and 34% at ages 16 to 18 compared with reference unvaccinated cohorts, reported Peter Sasieni, PhD, of Guy's Cancer Centre in London, and colleagues.

Similar estimated risk reductions were observed for the incidence of CIN3: 97% at ages 12 to 13, 75% at ages 14 to 16, and 39% at ages 16 to 18, they noted in .

Compared with the unvaccinated population, Sasieni and colleagues estimated that there were 448 fewer cases of cervical cancer than expected and 17,235 fewer cases of CIN3 than expected in the vaccinated cohort by June 30, 2019.

These results mirror those from a Swedish study that estimated that HPV vaccination reduced the chances of developing invasive cervical cancer by 88% over an 11-year period.

"We have shown that HPV vaccination with high coverage in 12-13 year old girls has almost eliminated cervical cancer and cervical precancer up to age 25 (the extent of the observed data)," the authors wrote. "Girls and women eligible for HPV vaccination should be encouraged to receive the vaccine, at any age but ideally when first offered it, to ensure that this hugely successful vaccination program continues to benefit younger generations."

This national HPV immunization program was introduced in 2008 and uses the HPV bivalent vaccine Cervarix. Since HPV vaccination is most effective when offered before HPV exposure, routine vaccination was offered to girls ages 12 to 13, with "catch-up" vaccination offered to those ages 14 to 18 over the following 2 school years.

While estimated relative reductions in cervical cancer seen in the study support the effectiveness of the vaccine, uptake continues to be an issue, noted Maggie Cruickshank, MB ChB, MD, of the University of Aberdeen in Scotland, and Mihaela Grigore, MD, PhD, of the University of Medicine and Pharmacy "Grigore T. Popa" in Lasi, Romania, in an .

"Even in a wealthy country, such as England with free access to HPV immunization, uptake has not reached the 90% vaccination target of girls aged 15 years set by WHO," they wrote. "COVID-19 is an additional challenge to delivering HPV vaccination but only adds to a long list, including access to affordable vaccines, infrastructure for low temperature-controlled supply chains, delivery, and waste disposal."

The problem of uptake is more pronounced in low- and middle-income countries where cervical cancer is a public health issue of particular concern, observed Cruickshank and Grigore. "The most important issue, besides the availability of the vaccine (related to the decision makers in the health policy), is the education of the population to accept the vaccination because a high rate of immunization is a key element of success."

Sasieni and colleagues analyzed population-based registry data from January 2006 through June 2019 for seven cohorts of women who were 20 to 64 years old by the end of 2019, including the three cohorts vaccinated at ages 12 to 13, 14 to 16, and 16 to 18 (to account for differences in the school year in which vaccination was offered), as well as earlier cohorts of women not eligible for vaccination.

Of the women eligible for vaccination at the ages of 12 to 13, 88.7% received at least one dose of vaccine, while 84.9% were fully vaccinated (three doses). Of those eligible at ages 14 to 16, 80.1% received at least one dose, and 73.2% were fully vaccinated, while 60.5% of those eligible at ages 16 to 18 received at least one dose, and 44.8% were fully vaccinated.

During the study period, there were 27,946 diagnoses of cervical cancer and 318,058 of CIN3.

Sasieni and colleagues acknowledged several limitations to the study, "the key one being that individual-level data for vaccination status were not available so we could not estimate individual-level efficacy."

They also noted that cervical cancer is rare in young women and therefore only a small number of cancers would have been expected in the absence of vaccination.

Comment