Adherence and Safety of the Human Papillomavirus (HPV) Vaccine in Bamako, Mali

Abstract

Background. In the absence of intervention, Mali, like many countries in sub-Saharan Africa, will face crisis in cervical cancer over the coming decades, as a very young population ages into higher-risk age groups. The human papillomavirus (HPV) vaccines have the potential to reduce the burden of cervical cancer, but only if implemented fully and effectively. Methods. Two HPV vaccine implementation strategies were tested in Bamako, Mali: a centralized clinic-based strategy, which resembled existing programs for other vaccines; and a novel, many-site, school-based strategy. The analysis considered a random sample of 150 adolescent girls recruited with each strategy, comparing the proportion within each program that adhered to the three-dose HPV vaccine. The study collected safety data at the second and third doses and between doses, and compared the rates of systemic adverse events to those seen in a Western, pre-license clinical trial. Results. The clinic-based and school-based programs achieved similar rates of three-dose adherence within 12 months (89% and 88%, respectively) and within the manufacturer-recommended windows (61% and 57%, respectively). Within each program, younger girls had higher rates of adherence. Neither program recruited an appreciable number of non-school-attending girls. Nineteen of 300 participants (6.3%) reported a systemic adverse event, which was significantly higher than the 2.6% of participants who reported a systemic adverse event in a pre-license clinical trial of the vaccine (p<0.01 for homogeneity; p=0.36 to reject of non-superiority margin of 5%). Conclusions. Public health planners in every setting in the developing world must carefully weigh the costs and benefits of each potential vaccination strategy. In Bamako, Mali, the many-site school-based HPV vaccination program offered a comparably effective alternative to centralized vaccination. The vaccine was generally well tolerated in this population, although systemic adverse events were reported at a somewhat higher rate than in a Western, pre-license clinical trial.