Effect of Vaccine Direct Delivery (VDD) on vaccine stockouts and number of vaccinations: Case study from Bauchi State, Nigeria.

Abstract Objective Vaccine stockouts are prevalent in Africa. Despite the importance of this as a barrier to universal vaccination coverage, rigorous studies looking at ways to reduce vaccine stockouts have been limited. We causally evaluated the effect of Vaccine Direct Delivery (VDD), an intervention to ensure the vaccine stock availability at health facilities, on the reduction of stockouts in Bauchi state, Nigeria. Methods Employing the interrupted time-series method, we evaluated the change in the occurrence of vaccine stockouts before and after the introduction of VDD in July 2015. We used health facility level data from January 2013 to December 2018 among 175 facilities in Bauchi state, collected through the District Health Information Software 2 (DHIS2) for monthly information on stockouts and stock balances in all the health facilities in Nigeria. Data were analyzed using Stata 15 SE. To validate the causal relationship between VDD and vaccine stockouts, we conducted two sets of robustness checks. First, we evaluated the effect of VDD on the stockouts of other commodities. Second, we compared the trend of the prevalence of vaccine stockouts among health facilities between Bauchi state where VDD was introduced and another state (Adamawa state) where VDD was never introduced. Results After the introduction of VDD, vaccine stockouts in Bauchi state decreased by 9 percentage points on average, and they have been decreasing monthly by 0.4 percentage points more than pre-VDD. In Adamawa state, where VDD was never introduced, the prevalence of vaccine stockouts did not change over time. In Bauchi state after VDD introduction, the stock balances of target vaccines all increased, and the number of vaccinations carried out increased in neighboring health facilities. Conclusions VDD intervention resulted in a significant reduction of vaccine stockouts as well as in an increase in the number of vaccinations performed. However, we should consider how to improve the system to provide vaccination service to the population in a sustainable way.