Canadian Medical Association Journal
Young women who received the human papillomavirus (HPV) vaccine
through a school-based program had fewer cervical cell anomalies when screened
for cervical cancer, found a new study in CMAJ (Canadian
Medical Association Journal).
"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," writes Dr. Huiming Yang,
Medical Officer of Health and Medical Director, Screening Programs, Alberta
Health Services, Calgary, Alberta, with coauthors.
Alberta has both a school-based HPV vaccination program and a
population-based screening program for cervical cancer.
In 2008, the province
introduced HPV vaccination for Grade 5 girls (aged 10-11) and a 3-year catch-up
program for Grade 9 girls (aged 14-15); in 2014, it was expanded to include
boys.
The program provides 3 doses of the vaccine that protects against two
strains of HPV, which account for 70% of all cases of cervical cancer.
To determine whether HPV vaccination had an impact on Papanicolaou (Pap) test results, Alberta researchers looked at data on the first cohort of women who participated in both the school vaccination program and cervical cancer screening.
The 10,204 women in the study population were
born between 1994 and 1997 (aged 18 to 21 years) and lived in the province
before 2008.
Of the total, 1481 (14.5%) were cases -- that is, they had
cervical anomalies detected during screening -- and the remaining 8723 (85.5%)
were controls -- with no cervical abnormalities detected.
Among cases, most
(1384, 93.5%) had low-grade cervical abnormalities, and the remaining 97 (6.5%)
had high-grade abnormalities.
More than half of the study participants (56%) were
unvaccinated, and 44% had received 1 or more doses of the HPV vaccine before
being screened for cervical cancer.
Of the women who had been vaccinated, 84%
received 3 or more doses. Among the unvaccinated women, 16.1% had cervical
abnormalities, compared with 11.8% in the fully vaccinated group.
The authors note that effective HPV vaccination with broad
uptake will affect the harms and benefits of cervical screening.
"With population-based HPV vaccination, guidelines for
cervical cancer screening may need to include a later age for screening
initiation age and/or a longer interval between screenings," they write.
The authors hope that their findings and future research will
lead to improved primary and secondary prevention efforts, with integration of
HPV vaccination and cervical cancer screening programs.