Two currently available human papillomavirus vaccines protect adolescents and young adult women without previous HPV disease from developing precancerous cervical lesions, according to data from more than 70,000 women followed for 8 years.
In a reviewby the Cochrane Library, , of the Belgian Cancer Centre, Brussels, and his colleagues examined the effectiveness of two vaccines that target the HPV types 16 and 18, which account for most cases of cervical cancer. The researchers focused on the bivalent vaccine for HPV16 and HPV18 and the quadrivalent vaccine for HPV16, HPV18, and two additional HPV types associated with genital warts (HPV6 and HPV11). The review did not include data on the latest vaccine targeting nine HPV types because it has not been studied in a randomized, placebo-controlled trial.
The review comprised 26 studies and 73,428 women aged 15-45 years. The vaccine was most effective for young women aged 15-26 years.
The risk of serious adverse events was approximately 7% in control groups and vaccine groups across all ages (669 per 10,000 vs. 656 per 10,000, respectively). The mortality rate was 11 per 10,000 in control groups, compared with 14 per 10,000 in vaccine groups. The overall mortality was low, and no deaths reported in the studies were vaccine related, the researchers said, although mortality was greater in the vaccine groups among women older than 25 years.
The overall risk for precancerous lesions was not significantly different for women vaccinated between age 24 and 45 years versus unvaccinated women. However, the researchers found that the vaccines reduced the risk of precancerous lesions for HPV type 16 and 18 from 45 per 10, 000 to 14 per 10,000 in women aged 24 years and older who were previously negative for HPV 16 and 18.
The researchers found no significant impact on miscarriage rates, but they noted the need for additional research to examine the possible impact of vaccination on stillbirth and birth defects in children born to women who were vaccinated during pregnancy.