A new study indicates that the human papilloma virus vaccine, Cervarix, not only has the potential to prevent cervical cancer, but is also effective against other common cancer-causing human papillomaviruses — aside from just the two HPV types, 16 and 18, which are responsible for about 70 percent of all cases.
That effectiveness endured for the study’s entire follow-up, of up to four years, according to the researchers. The findings, based on a multinational clinical trial involving nearly 20,000 young women, were published February 4 in Clinical and Vaccine Immunology, a journal of the American Society for Microbiology.
“The study confirms that targeting young adolescent girls before sexual debut for prophylactic HPV vaccination has a substantial impact on the incidence of high grade cervical abnormalities,” said Dr. Dan Apter, a co-author of the study and the director of the Sexual Health Clinic at Family Federation of Finland in Helsinki.
HPV is the most common sexually transmitted virus in the United States. About 75 to 80 percent of sexually active men and women are infected at some time in their lives. Most HPV infections don’t cause any symptoms, and go away on their own. But HPV can cause cervical cancer in women, as well as several other types of cancer in both men and women.
The new study is the last in a series of reports from the Papilloma Trial Against Cancer in Young Adults (PATRICIA), a multinational clinical trial encompassing 14 countries in Europe, the Asia-Pacific region, North America, and Latin America, and it confirms previous reports in this trial. The overall trial constituted the basis for approval of the Cervarix vaccine in Europe and the United States.
Vaccination is most effective when delivered early
The vaccine was found to be extremely effective in young women who had never been infected with HPV. It protected nearly all from HPV-16 and -18, and protected 50-100 percent against different grades of precancerous transformation of cervical cells caused by other strains of HPV, including up to 100 percent of those with the immediate precursor grade to cancer. The women were followed for up to four years post-vaccination.
The vaccine was distinctly more effective among young women ages 15-17 than those ages 18-25, underscoring the value of vaccinating young adolescents, said Dr. Apter. The lower efficacy in the oldest age group may result from a larger proportion of women in that age group having had persistent infections at the time of vaccination, he said.
While the trial did not investigate the vaccine’s efficacy in males, sexually transmitted HPV causes anogenital and head and neck cancers in both males and females. HPV-related head and neck cancers now number around 8,400 in the US, annually. “The more adolescents are vaccinated, the closer we will be to eradicating high risk HPV viruses,” said Apter. “So I think boys should also be vaccinated.”
Cervical cancer is the fourth most common cancer among women, with estimates from 2012 indicating that there are 528,000 new cases and 266,000 deaths each year worldwide; the majority of these cases occur in developing countries. In the U.S., about 12,000 new cases, and 4,000 deaths occur annually, according to the SEER database of the National Cancer Institute.
“It is now established that having a persistent infection with HPV is a necessary cause of cervical cancer,” said Dr. Apter, highlighting the importance of early HPV vaccination for future cancer prevention.
Federal guidelines call for all boys and girls to get three doses of the HPV vaccine, starting at age 11 or 12. But most aren’t following those recommendations. Only a third of girls who should have finished the series have received all three doses, and the record’s even worse for boys. While 57 percent of pre-teen or teen girls have received at least one dose of HPV, only 35 percent of boys have, according to the Centers for Disease Control and Prevention.