A Scottish observational study on the effectiveness of the human papillomavirus vaccine shows that no cases of cervical cancer were recorded in women immunized at 12 or 13 years of age. In addition, researchers observed a significant reduction in incidence of cervical cancer in the 14 to 22 age group compared with unvaccinated women.
The population-based study linked screening, vaccination and cancer registry data collected across Scotland to assess HPV vaccine efficacy. Researchers extracted data for women born between January 1988 and June 1996.
The types of vaccine administered to the cohorts of women monitored in the study changed over time as newer ones became available. Each newer generation vaccine targets more types of HPV. Until 2012, the vaccine most in use was the bivalent Cervarix. Subsequently, the quadrivalent Gardasil was administered until last year when the 9-valent Gardasil was introduced.
Scotland began routine immunization in schools in 2008. Illustrative of the success of the school campaign is the fact that by the time students in the 2022-2023 school year were in their fourth form of secondary school (equivalent to 10th grade in the U.S.), nearly 90% had received at least one dose of the vaccine.
By contrast, in the U.S., where HPV vaccines are not administered in school, uptake among adolescents is considerably lower at around 60%.
HPC causes six types of cancer, including cervical cancer. The virus also causes genital warts. HPV is the most common sexually transmitted disease among women.
In the U.S. about 14,000 new cases of invasive cervical cancer are diagnosed annually and almost 4,400 women die from the disease.
Worldwide the disease burden is substantial. According to data posted by the World Health Organization, cervical cancer is the fourth most common cancer in women globally with an estimated 604,000 new cases and 342,000 deaths in 2020. The highest rates of cervical cancer incidence and mortality are in low- and middle-income countries, which is driven by lack of access to HPV vaccines, cervical screening and treatment services.
The vaccines prevents more than 90% of HPV-attributable cancers. Prophylactic vaccination against HPV, as well as evaluation and treatment of possibly precancerous lesions are effective ways to prevent cervical cancer. HPV vaccination is given as a series of either two or three doses, depending on age at initial vaccination.
The U.S. Centers for Disease Control and Prevention recommends routine vaccination at ages 11 or 12 and immunization for everyone through age 26 provided they haven’t been adequately vaccinated when younger. But vaccination is generally not recommended for those older than 26. A main reason for this is that a large number of people in this age range have already been exposed to HPV.
According to an NBC News report, owing to early detection and treatment, rates of cervical cancer have descended in the U.S. by more than 50% since the 1960s. Rates are declining particularly fast among women in their early 20s, the first generation to benefit from HPV vaccines.
However, it’s worrisome that among women in their 30s and early 40s, incidence has recently been ticking up. Diagnosis of cervical cancer among women ages 30 to 44 rose almost 2% annually from 2012 to 2019.
What’s especially unsettling is that in America more than 50% of women diagnosed with cervical cancer have either never been screened or haven’t been evaluated in the past five years, according to the CDC. During screening exams, doctors can identify the presence of HPV and find, remove and analyze possibly precancerous lesions.
Overall, the National Cancer Institute estimates that the number of women ages 21 to 65 who have been screened fell from 87% in 2000 to 72% in 2021.
The U.S. Preventive Services Task Force recommends screening women ages 21-29 with Pap smears every three years. The Pap smear looks for abnormal cells in the cervix. Women ages 30 to 65 can be screened either every three years with a Pap smear or every five years with a cervical screening test used to detect HPV or a combination of a Pap smear and HPV test.
After screening, it’s vital that those who have abnormal results receive follow-up care. However, in a study published last year in the American Journal of Preventive Medicine, researchers found that only 73% of women did.
There are subtle differences between the U.S. and Scottish approaches to screening. In Scotland, the National Health Service invites women between the ages of 25 and 64 for routine screening every five years. If a previous test detected HPV, the frequency of screening is increased and samples of cells from the cervix are tested for abnormality. But it is no longer standard for such samples to be examined under a microscope for abnormal cells.
The much bigger distinction in course of action is the incorporation of routine HPV immunization in Scottish schools, something that is not done in the U.S. Judging from the study findings, Scotland’s method appears to be having a positive health impact.