Study designs of evaluations included in the review
Randomised controlled trials (RCTs) were eligible for inclusion.
Specific interventions included in the review
Studies of any vaccine against HPV that contained at least one oncogenic strain of the virus, used prophylactically, were eligible for inclusion. Any dosing regimen was accepted. Studies with reports of therapeutic vaccination were excluded, as were those not designed to address outcomes related to vaccine efficacy against oncogenic HPV strains. Comparators were required to be either placebo or ‘no HPV vaccination’.
Participants included in the review
Studies in women receiving the HPV vaccine were included. There were no exclusions on the basis of age or other demographic characteristics. The women in the included studies had a mean age of 20 years (age range: 15 to 25).
Outcomes assessed in the review
The primary outcome of interest was the frequency of high-grade cervical lesions (defined as high-grade squamous intraepithelial lesion, or grade 2 or 3 cervical intraepithelial neoplasia). The secondary outcomes reported included persistent HPV infection, low-grade cervical lesions, external genital lesions, adverse events and death.
How were decisions on the relevance of primary studies made?
The two primary reviewers independently screened studies for relevance. Any discrepancies were resolved through consultation with a third-party reviewer.