Human papillomavirus infections among sexually active young women in Uganda : Implications for a vaccination strategy

Introduction: Information about the genital (human papillomavirus) HPV infection is needed to support the introduction of HPV vaccination in Uganda. Objectives: (i) To estimate the prevalence, incidence, clearance and to evaluate the associated risk factors for the genital HPV infection. (ii) To evaluate in a pilot study the possibility of using filter paper to collect, store and transport cervical material for HPV DNA testing and genotyping. Subjects and Methods: We conducted two clinic-based prospective cohort studies between September 2002 and December 2006. We consecutively recruited 1,275 sexually active women among those seeking services at Naguru Teenage Information and Health Centre (NTIHC) and 1,097 consecutive young primigravidae from those seeking pre-natal care at Naguru Health Centre (NHC) in Kampala, Uganda. Women were followed up for an average of 18.5 months (range 9.7-26.6). Detailed information on socio-demographic characteristics, reproductive and menstrual factors, sexual behaviour, history of sexually transmitted diseases of the women and their sexual partner(s), use of contraceptive methods and other lifestyle characteristics was obtained at baseline and follow up using interviewer administered standardized questionnaires. Cervical exfoliated cells were collected in Phosphate Buffer Saline (PBS) or PreservCyt solution as well as on filter paper. A sensitive PCR assay (SPF10/LiPA) was used to detect 42 different genital HPV types. Results: In Paper I, only 32.4% of HPV types determined with filter paper were verifiable with PBS (kappa statistic = 0.18). Multiple HPV types were detected in 54.1% of PBS compared to 15.3% of filter paper samples. Infections with ≥ 4 HPV types were 18.0% in PBS compared to2.7% in filter paper samples. In Paper II, the prevalence of HPV and HIV infections was 74.6% and 8.6%, respectively. High-risk HPV (HR-HPV) types were found in 51.4% of the women. The most frequently detected HR-HPV types were 51, 52, 18 and 16. Multiple infections were frequent. HIV positive women had a higher HPV prevalence (87.8%) and multiple infections (64.6%) than HIV negative women, 73.2% and 37.3%, respectively. Employment in the tertiary sector, lifetime number of sexual partners, a positive pregnancy test and detection of genital warts were significantly associated with HPV positivity. In Paper III, the incidence rate of HPV infections was 30.5 per 100 person-years. The risk for incident infections was not statistically significant among HIV positive compared to HIV negative women (Risk Ratio, [RR] = 2.8, 95%; 95% Confidence Interval [CI]; 0.9-8.3). Clearance for the individual HPV type was frequent; 42.3-100.0 % for HR-HPV types and 50-100% for low-risk types. HIV negative women cleared their infection more frequently than HIV positive women (clearance Adjusted = 0.2, 95% CI = 0.1-0.7). In Paper IV, the prevalence of HPV infections was 60% among young primigravidae. HPV 16 and 18 were detected in 8.4% and 5.8%, respectively, which was less frequent than HPV 51 (8.7%) and HPV 52 (12.1%). Although HPV infections were detected in 42.9% of women between the 1/2 and 3 trimesters, and 38.1% between pregnancy and delivery, 50.0% and 71.8% of HPV infections, respectively cleared, leaving the HPV prevalence unchanged in different periods of pregnancy. Conclusion: The prevalence and incidence of high-risk HPV infections were extremely high in our study populations of young women in Kampala, Uganda. Clearance of HPV infections was frequent but had no effect on prevalence.