A vaccine for human papillomavirus (HPV) can almost entirely prevent cervical cancer and precancers if given to girls early enough, a U.K. study published in the Lancet on Wednesday evening suggests.
Researchers from King’s College London found an 87 per cent relative reduction in cervical cancer among women who had received the Cervarix HPV vaccine when they were 12 or 13, compared to the expected rate among unvaccinated women.
There was a 62 per cent reduction among those who had received their shots between the ages 14 and 16, and a 34 per cent reduction among women who were immunized when they were 16 to 18 years old.
The peer-reviewed study also showed significant reductions in non-invasive cervical carcinoma (CIN3) — a type of cervical precancer — ranging from a 39 per cent reduction in women who had received the HPV vaccine between age 16 to 18, to a 97 per cent reduction for those immunized at age 12 or 13.
“Our findings should greatly reassure those still hesitant about the benefits of HPV vaccination,” the study authors said.
“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).”
For this observational study, the researchers examined data from a population-based cancer registry. They looked at cervical cancer and precancer assessments conducted between Jan. 1, 2006 and June 30, 2019 in women between 20- and 64-years old.
All the women lived in the U.K., which began its school-based HPV immunization program in 2008. The older generations represented in the data would not have had access to HPV vaccination.
The researchers estimated that between 2006 and 2019 there had been approximately 448 fewer than expected cervical cancers and 17,235 fewer than expected cases of the CIN3 precancer among those in the vaccinated cohorts.
‘Very exciting study’
Cervarix protects against two strains of HPV associated with cervical cancer (Type 16 and Type 18). The Gardisil and Gardisil 9 vaccines are more commonly used in Canada, which started its school-based HPV vaccination program in 2007.
But the study’s results are relevant in this country too, said Dr. Amanda Selk, an obstetrician-gynecologist at Mount Sinai Hospital in Toronto. She was not involved in the British research.
“It’s a very exciting study, because it’s the first study that’s actually shown the HPV vaccine can prevent cervix cancer. All previous studies have shown that the vaccine can prevent the precancers,” said Selk, who is also president of the Society of Canadian Colposcopists. (Colposcopists examine the cervix.)
The results aren’t a surprise, she said, but the study provides additional proof of the vaccine’s importance — and may help convince parents who have been hesitant to have their children vaccinated.
“Many of us assumed it prevented cancers, but there were non-believers who wanted to see the cancer data. So here it is. Now we have it,” she said.
According to the Canadian Cancer Society, more than 1,400 people in Canada are expected to be diagnosed with cervical cancer in 2021 and about 380 will die from it. Both the society and the World Health Organization say nearly all cervical cancers are preventable, and have called for increased uptake of the HPV vaccine.
Dr. Allan Covens, head of gynecologic oncology at Sunnybrook Health Sciences Centre in Toronto, said the British study is “significant” for Canada.
“Both countries have adopted mass vaccination for young women,” Covens, who also was not involved in the U.K. study, said.
“So we can expect to see similar results in reduction in not only cervical cancer, but also precancerous changes [in cervical cells].”
The goal, Covens said, is to vaccinate young people before they become sexually active and are exposed to HPV. In addition, the younger someone is, the more robust their immune response to the vaccine is expected to be.
“We have the ability to prevent cervical cancer. Cervical cancer is related to a viral infection, and we can mitigate and prevent it with simple vaccination,” Covens said.
“It’s a safe vaccine and we’ve proven that it does exactly what it has been claimed to do,” Covens said.
Continued followup needed
The U.K. researchers acknowledged some limitations in their study, including the fact that since the HPV immunization program only started 13 years ago, the vaccinated population is still young and therefore would be less likely to be diagnosed with cervical cancer anyway.
Because cervical cancer is rare in young women, more followup as they grow older is needed, they said.
However, Type 16 and Type 18 HPV are found in up to 92 per cent of “women diagnosed with cervical cancer before the age of 30,” the authors said in a news release.
Despite the limitation, the study results are still significant, both Covens and Selk said.
In fact, the benefits could be even greater than the results suggest, they said, because the researchers only looked at outcomes for those who had received the Cervarix vaccine.
Gardisil also protects against HPV Types 16 and 18, and two types that cause genital warts. Gardisil 9 also protects against five additional HPV strains that can cause cervical cancer.