Using oral polio vaccine beyond the cold chain: A feasibility study conducted during the national immunization campaign in Mali

We conducted the first systematic documentation of using oral polio vaccine (OPV) out of the cold chain during national immunization day (NID) campaigns in Mali. Using a crossover intervention design, vaccinators compared the transport of OPV in vaccine carriers with or without ice packs. Vaccine integrity was assured through monitoring vaccine vial monitor (VVM) status. Despite ambient temperatures up to 40 °C, none of the VVMs on any of the vials used (n = 956) reached their discard point. Over 90% of vaccinators and supervisors preferred conducting NIDs without ice packs. In addition, using OPV out of the cold chain reduced vaccine wastage resulting from melting ice packs causing labels to detach from the vial.