To determine baseline HPV prevalence in unvaccinated women and predict impact of HPV vaccination on high-grade cervical disease (CIN2+).
A pseudo-anonymous prospective cohort was sampled on entry to the routine cervical screening programme between March 2009 and November 2010. In total, 13,306 eligible females were identified and high-risk (hrHPV) type specific status determined. Potential impact of prophylactic vaccination on CIN2+ was calculated by applying HPV vaccine clinical trial data to the baseline HPV type-specific data.
Of 13,306 samples tested, 3545 (26.6%) were confirmed positive for at least one hrHPV type and 1325 (10%) were positive for low risk HPV. HPV16 was the predominant type detected in cases positive with either single or multiple hrHPV infection(s) (5.2% and 4.7%, respectively). Based on hrHPV type-specific data, Gardasil would have prevented 33.2% HPV16/18 unrelated CIN2+ compared to 47.1% for Cervarix. This difference was not statistically significant.
Prior to the introduction of the HPV vaccine, approximately one-quarter of young women were positive for hrHPV and one-tenth positive for HPV16. Post-vaccination, we anticipate a substantial absolute risk reduction in high-grade cervical disease associated with both targeted and non-targeted hrHPV types. There is no significant difference between the two commercially available vaccines in terms of clinical impact.