Estimation and Monitoring of the Potency of bOPV Stored at Different Temperatures over a Period of Time

Background: Poor storage of the polio vaccine in areas of inadequate or absent power to sustain the cold chain can compromise its potency. This study assessed the sustainability of the bOPV vaccine potency using viral titer and the colour of the vaccine vial monitor (VVM) when stored in the refrigerator, room, incubators, and at atmospheric temperatures over time. Method: The standardized World Health Organization (WHO) protocol was used to determine the vaccine titers weekly until the VVM degraded to 100%. Weekly average temperatures of the vaccine storage conditions were also obtained. Results: The fifty vials of bOPV tested before exposure had titers above the WHO minimum values, and VVM rated at 0% degradation. Eight of ten vials of bOPV stored in the refrigerator sustained potency for six months, with the color of VVM at 0% and 10% in five and six months, respectively. At room temperature, nine of ten vaccine vials retained potency up to three weeks, and the VVM degradation rates were 10 %, 20%, 40% and 100% after one, two, three, and four weeks, respectively. The potency of twenty vials of bOPV in the incubator was sustained for a week, and the VVM degraded by 10%, 50% and 100 % at one, two, and three weeks, respectively. At atmospheric temperature, the titers significantly dropped, and the VVM was at 100% degradation within a week. Conclusion: The potency of bOPV was most preserved under refrigeration, moderately compromised at room temperature, and severely degraded at incubator temperatures over time.