A Danish study finds that vaccination against the human papillomavirus is associated with reduced rates of precancerous cervical lesions in young women.
The results of a new study conducted in Denmark add to evidence suggesting that the human papillomavirus (HPV) vaccine is effective in protecting women against cervical cancer
. The study
, published online on February 19, 2014, in the Journal of the National Cancer Institute
, found a reduced risk of precancerous cervical lesions in young women just 6 years after the introduction of the quadrivalent HPV vaccine.
The quadrivalent vaccine, which protects against 4 strains of the virus, was licensed in 2006 in Denmark and was later included in the Danish childhood vaccination program. To assess the efficacy of the vaccine, the nationwide study evaluated the relationship between individual vaccination status and risk of cervical lesions among young women born between 1989 and 1999. Using national health registries, the researchers identified the HPV vaccination status of all girls from 2006 to 2012. Information on all cervical examinations for the women included in the cohort was collected and used to identify incident cases of cervical lesions.
Of 399,244 young women included in the analysis, 247,313 (62%) were vaccinated by the end of the study period. Vaccination coverage was highest among younger girls born from 1993 to 1999, who were included in the vaccination program. The results indicated that women who had received the vaccine were less likely to develop cervical lesions. Overall, unvaccinated women were 2.4 times more likely to be diagnosed with atypia or worse and were twice as likely to be diagnosed with cervical intraepithelial neoplasia grade 2 or 3 (CIN 2/3) than were vaccinated women.
When analyzed by age, vaccinated girls born from 1991 to 1994 had a significant reduction in risk for atypia or worse and for CIN 2/3. Among vaccinated women born from 1989 to 1990, the risk for atypia or worse was significantly lower, and the risk of CIN 2/3 was decreased, although this reduction was not statistically significant. No cervical lesions occurred in girls born between 1997 and 1999. Across all age groups, vaccinated women had higher rates of screenings than did unvaccinated women.
The study authors suggest that the smaller risk reduction observed among older women may be due to a higher prevalence of HPV infections before introduction of the vaccine. “[O]ur results show that vaccination with the quadrivalent HPV vaccine is already effective in reducing the risk for cervical precursor lesions at population level among young women in Denmark,” they conclude.
Despite these findings and previous research indicating the efficacy of the vaccine
, rates of vaccination against HPV remain low in the United States
. Two HPV vaccines are currently available—Gardasil and Cervarix—and a 3-dose course of either is recommended for all females aged 11 to 26. Vaccination with Gardasil is also recommended for males aged 11 through 21.