Nevertheless, the missing piece of the puzzle was data on cervical abnormalities, which Alberta Health Services' Dr Huiming Yang has provided. "Eight years after a school-based HPV vaccination program was initiated in Alberta, 3-dose HPV vaccination has demonstrated early benefits, particularly against high-grade cervical abnormalities, which are more likely to progress to cervical cancer," Yang and co-authors wrote.
From a sample of 4,538 women who were among the first to receive the Gardasil vaccine in 2008, 11.8 percent had cervical abnormalities, while the figure was 16.1 percent for their unvaccinated contemporaries. Most of these abnormalities were considered “low-grade” and unlikely to lead to cancer; women who had not been vaccinated were more than twice as likely to have “high-grade” abnormalities.
The presence of abnormalities even among vaccinated women is unsurprising since the vaccine does not protect against all strains of the virus. Consequently, it remains important for vaccinated women to get pap tests, although the authors suggest consideration should be given to conducting these less frequently.
Alberta is unusual in extending the Gardasil vaccination program to boys, both to prevent them from transmitting the disease to partners and to protect against penile and anal cancers, which are often also caused by HPV.
Girl getting the Gardasil vaccine. Image point Fr/Shutterstock