The HPV vaccine appears to be doing what it was intended to do—lowering rates of cervical cancer, particularly HPV types 16 and 18, responsible for most cases worldwide.
Since 2006, when a vaccine for human papillomavirus (HPV) was first offered in the United States, the goal of the medical community was to reduce rates of cervical cancer and other HPV-linked diseases. The vaccine appears to be doing just that, according to the results of a recent study by investigators at the US Centers for Disease Control and Prevention (CDC).
The study involved analyzing data collected from 5 different sites through the HPV Vaccine Impact Monitoring Project (HPV-IMPACT), which monitors trends in cervical precancer in women between the ages of 18 and 39. The investigators were particularly interested in discerning the impact of the HPV vaccine on HPV types 16 and 18, which cause 7 out of 10 cases of cervical cancer worldwide. They found that the total number of cases of adenocarcinoma in situ, or CIN2+, in vaccinated women in HPV-IMPACT’s database dropped from 2344 in 2008 to 1857 in 2014—a nearly 22% decline. CIN2+ cases definitively caused by HPV16/18 also declined, from 1235 cases in 2008 to 819 cases in 2014.
The study counted vaccinated women as those who received at least 1 dose of the HPV vaccine, although most women in that category did receive all the necessary doses, according to the study’s investigators.
“Other studies are being done to determine whether 1 dose of HPV vaccine is sufficient, but we cannot conclude anything about the effectiveness of different numbers of doses from this study,” Nancy McClung, PhD, RN, epidemic intelligence officer at the CDC and an author of the study, told Contagion®. “The most important point to understand is that the proportion of HPV16/18-positive CIN2+ decreased more in women known to be vaccinated than in all women who were not vaccinated or had unknown vaccination status. This is evidence that the vaccine is working to decrease cervical disease in young women.”
The investigators also found a decline in HPV rates among unvaccinated women, which they attribute to the benefits of herd protection.
HPV vaccine rates have increased over the years, but the vaccine is still a tough sell compared with many other vaccines such as the one for measles, mumps, and rubella (MMR). Studies show that roughly half of all adolescents have completed the full course of the HPV vaccine, which consists of 2 or 3 doses depending on the age at which it’s started. The original vaccine offered in the U.S. was a quadrivalent vaccine, offering protection against HPV types 6 11, 16 and 18. “The current vaccine administered in the United States is the 9-valent vaccine, which protects against an additional 5 cancer-causing HPV types (HPV 31/33/45/52/58),” said Dr. McClung. “About 15% of cervical cancers are attributable to these 5 types.”
Dr. McClung’s colleague at the CDC and a member of the current study team, Julia Gargano, PhD, has conducted research on males with HPV, and her findings indicate that the vaccine seems to be reducing cancer levels in males along with females.
According to the CDC, HPV is the most common sexually transmitted infection in this country, with 79 million people infected with it. Normally it goes away without causing any problems, but it can cause anogenital warts and cervical, penile, and other types of cancers. Current recommendations are for all 11 and 12 years old in the U.S. to receive the vaccination, with catch-up vaccinations available for people in their teens and 20s.