Coverage and cost of a large oral cholera vaccination program in a high-risk cholera endemic urban population in Dhaka, Bangladesh

Abstract

A feasibility study of an oral cholera vaccine was carried out to test strategies to reach high-risk populations in urban Mirpur, Dhaka, Bangladesh. The study was cluster randomized, with three arms: vaccine, vaccine plus safe water and hand washing practice, and no intervention. High risk people of age one year and above (except pregnant woman) from the two intervention arms received two doses of the oral cholera vaccine, Shanchol™. Vaccination was conducted between 17th February and 16th April 2011, with a minimum interval of fourteen days between two doses. Interpersonal communication preceded vaccination to raise awareness amongst the target population. The number of vaccine doses used, the population vaccinated, left-out, drop out, vaccine wastage and resources required were documented. Fixed outreach site vaccination strategy was adopted as the mode of vaccine delivery. Additionally, mobile vaccination sites and mop-up activities were carried out to reach the target communities. Of the 172,754 target population, 141,839 (82%) and 123,666 (72%) received complete first and second doses of the vaccine, respectively. Dropout rate from the first to the second dose was 13%. Two complete doses were received by 123,661 participants. Vaccine coverage in children was 81%. Coverage was significantly higher in females than in males (77% vs. 66%, P<0.001). Vaccine wastage for delivering the complete doses was 1.2%. The government provided cold-chain related support at no cost to the project. Costs for two doses of vaccine per-person were US$3.93, of which US$1.63 was spent on delivery. Cost for delivering a single dose was US$0.76. We observed no serious adverse events. Mass vaccination with oral cholera vaccine is feasible for reaching high risk endemic population through the existing national immunization delivery system employed by the government.

Climate-driven endemic cholera is modulated by human mobility in a megacity

“…The heterogeneous physical landscape of the city, implicitly captured here via population density, could not only be an explanation of the different sensitivity to ENSO between the core and the periphery as suggested by [13], but also yields predictions of mobility fluxes that act to spread the disease. By providing insight into the spatial nature of transmission, the increased understanding these processes may help in the design of large-scale vaccination campaigns supported by promising field studies [29, 30]. …”

“…Addressing the interplay between climate forcing and spreading mechanisms could prove useful in designing vaccination campaigns that take spatial structure into account, especially given the recent evidence showing the feasibility and protective effect of this kind of intervention in Dhaka [29, 30]. Indeed cholera models that account for spatial connectivity have been proposed to guide reactive vaccination interventions during urban cholera epidemics [31].…”

Economics and financing of vaccines for diarrheal diseases

“…[43][44][45][46] One study evaluated different immunization strategies and looked at the impact of herd immunity, 44 while two studies evaluated the cost of a mass vaccination campaign -determining the total cost, cost per person (ranging from $3.93 to $30 per fully immunized person) and potential cost-savings. 43,46 These estimates varied with cost inclusions, for example $3.93 is for the vaccine only, while the $30 figure includes other components of the campaign (only 68% of this was vaccine cost).…”

“…For example, the cost per vaccine dose tends to be a key parameter in economic evaluations, and these studies utilized values that may not be comparable-ranging from $0.60 to $5 per dose, while in others it was calculated based on program costs for vaccination campaigns. While these studies had several strengths (e.g., evaluated relevant populations, 43,44,46 large populations/sample size, 46 included appropriate costs and factors impacting vaccination and costs, 43,44,46 performed sensitivity analysis, 44 explored various realistic scenarios, 44 and had appropriate cost inclusions 44 ), limitations include interviews and questionnaires to gather costs (which may incur recall bias), 43,44 no probabilistic sensitivity analysis were performed in one study, 43 and the effects of waning immunity were not considered (although this most likely would have a little effect). 43,44 Additionally, herd protection is location specific, and with limited data, assumptions were made.…”

“…43,44 Additionally, herd protection is location specific, and with limited data, assumptions were made. 44 Evaluation of an actual campaign 43,46 can be helpful, but also limits generalizability to areas with other target populations, disease incidence, and other key factors.…”