Association of vaccine stockout with immunisation coverage in low-income and middle-income countries: a retrospective cohort study

OBJECTIVES: This study investigated the association between vaccine stockout and immunisation coverage, and infant/under 5 mortality rates. DESIGN: A retrospective cohort study. SETTING: Low-income and middle-income countries. PARTICIPANTS: A cohort of 131 low-income and middle-income countries from 2004 to 2019. PRIMARY OUTCOME MEASURES: Main outcomes included immunisation coverages of (1) diphtheria-tetanus-pertussis containing vaccine (DTP), (2) measles containing vaccine (MCV), (3) BCG and (4) oral polio vaccine (OPV). We also included infant and under 5 mortality rates as secondary outcomes. RESULTS: The countries that experienced national-level stockouts of DTP and MCV had 3.7 and 4 percentage points lower coverage rates of DTP3 and MCV1, respectively, compared with the countries without the stockout events (p<0.01). Moreover, the statistically significant differences in the immunisation coverage rates across the countries with and without the stockout events are 2.4 percentage points and 2.6 percentage points for BCG and OPV, respectively (p<0.01). CONCLUSION: Our findings show that the incidence of vaccine stockout events is associated with the decreased immunisation coverages for children in low-income and middle-income countries. However, we did not observe a statistically significant association between the increasing frequency of vaccine stockout and infant and under 5 mortality rates.