A generational study conducted by the University of Copenhagen, Denmark, compared the health outcomes of the first group of women to receive the HPV vaccine as part of Denmark’s childhood vaccination schedule, to women born a decade earlier who didn’t receive the vaccine. The vaccine works, it concludes, having lowered the incidence of severely abnormal, potentially precancerous cervical tissue by 40% between the two generations.

“It is the first study in the world to test the Gardasil-4 vaccine on a population level. The childhood vaccination program, which includes the HPV vaccine, is targeted at the entire population. Therefore, it is important to look at the entire population and the effect of the vaccine after the first screening of women aged 23 years,” says Elsebeth Lynge, a professor in the department of public health at the University of Copehagen.

The study, published in the International Journal of Cancer, compared the results of cervical screenings at age 23 for women born in 1983 and 1993; women in both groups had similar levels of education and average age of sexual debut, as well as other potentially influencing factors.

The 40% drop in severe cases of abnormal cervical tissue “means that fewer women have to be referred to a gynecologist for further examination and have a tissue sample taken. Eventually, we also expect fewer to fall ill,” explains Lise Thamsborg, a PhD student and study author.

The researchers came across one surprise: Among vaccinated women born in 1993, there was a higher number of cases of mildly abnormal cervical tissue than among unvaccinated women born in 1983. The researchers attribute this to improved, more sensitive analyzing technology that can identify mild cases more accurately — technology that was likely unavailable to the women born in 1983 at the same age.

While girls from the 1993 group received the vaccine at age 15, researchers say the effects of the vaccine will likely be much pronounced today and in the future, as Denmark has lowered the recommended age of HPV vaccination to 12, when few children are already sexually active.

Presently, the HPV vaccine is not yet included in India’s national immunization program, and some leading medical authorities perpetuate the misconception that screenings are as effective and convenient as vaccination. But progress is being made; an HPV vaccine program is underway for schoolgirls in Delhi. Hopefully, in time, India, which presently accounts for one-fourth of the world’s cervical cancer cases, will see a similar significant decline.