Strategies to involve youths in influenza vaccination programs and campaigns will be essential to achieve better national coverage. “
“Vaccines included in the Expanded Programme on Immunization (EPI) are sensitive to heat and lose their potency if exposed to high temperatures over long time. Therefore, it is recommended to keep them in a temperature-controlled supply chain (between 2 and 8 °C) [1]. Maintaining this cold chain under field conditions is frequently challenging where there is a lack of fridges, ice packs, electricity and efficient transport infrastructure. The effort to assuring

cold chain conditions can be a major factor limiting the flexibility for the vaccination teams and their access to the entire population [2] and [3]. Vaccine vial MK0683 monitors (VVMs) are small heat- and time-sensitive stickers attached to each individual vial of WHO-prequalified vaccines [4]. They gradually change colour as a vial’s cumulative exposure to heat increases. Once 5-Fluoracil datasheet the vial has been exposed to so much heat that the vaccine’s potency can no longer be assured, the inner square

on the VVM changes to a dark colour. When the inner square achieves the same colour as the outer circle, the VVM endpoint is reached and the vaccine should be discarded. VVMs allow users to know whether the vaccine in a given vial remains sufficiently potent such that it should be used, even in situations where the cold chain cannot be guaranteed [5] and [6]. Fig. 1a illustrates the VVM standard classification. Previous studies have demonstrated the correlation between the degree of colour change in the VVM and the potency (i.e. level of content of active ingredient, attenuated Adenylyl cyclase poliovirus) of the vaccine [7], [8] and [9]. Different types of VVMs are manufactured

in order to match the varying stability profiles of vaccines. Oral Polio Vaccine (OPV) is the most heat-sensitive of the EPI vaccines and is equipped with a VVM2, which reaches its endpoint after a cumulative exposure to 37 °C for up to 2 days [6]. National immunization days (NIDs) are organised as part of the global goal of poliomyelitis eradication, targeting all children under 5 years of age [10]. Ideally, during vaccination activities, the vaccinators should use cool boxes with ice packs for transporting the OPV to prevent the vaccine’s exposure to heat. Countries where polio transmission and import still occur often face challenges in securing enough vaccine carriers and ice packs to support the campaign outreach activities. In this situation, WHO and UNICEF recommend flexible polio vaccine management and guidance for this approach has been published [6] and [11]. These guidelines outline the procedures for storing OPV so as to ensure potency and quality when maintaining the standard 2–8 °C is not possible.