This field-level data is a key component in ensuring the policy changes and licensing sought are compatible with country needs and conditions. Assessment of the vaccine usability was based on the status of the VVM on the OPV vials. Laboratory studies and field studies conducted mainly in India have shown good correlation check details between the OPV potency (level of active ingredient) and the VVM stage following exposure of the vaccine to heat [7], [8] and [9]. Nevertheless, in order to obtain certainty that the vaccines delivered during these NIDs did in fact retain the assumed potency levels, a study measuring the remaining virus content levels would be required. The sample selection

was based on convenience, taking into account the logistical and practical constraints of organising the study. Nevertheless, the four health areas that participated are a likely good representation of the six areas of the Sélingué

district selected for the investigation. They cover more than half of the geographical area and inhabitants of the district. During this study, teams had the opportunity to use and experience both methods. This way, each vaccination team performed as its own comparison group www.selleckchem.com/products/AC-220.html for the two procedures that were applied, preventing a potential systematic difference between OCC/CC groups. The teams were therefore aware of the purpose and objective of investigation. Consequently, it is possible that there was a systematic difference in the perceptions of the participants concerning the new method introduced. The risk

of respondent bias, i.e. participants responding what they think will please the interviewers, was reduced by a neutral and independent approach to data collection [13]. Questions were phrased and administered in an impartial way, and there was no judgement or incentive related to responses. Furthermore, the weight mafosfamide reduction through the OCC procedure, which was the main reason for vaccinators to prefer this procedure, is undisputable. Nevertheless, a small element of respondent bias in this more qualitative part of the study cannot be fully excluded. One of the main concerns in planning the study was ensuring that none of the vaccines administered had an expired VVM. To prevent this from happening, prior training was conducted and supervision during the vaccination activities was assured. Further, the teams only used the polio vials kept outside of the cold chain for one day at a time (whereas stability data indicate that OPV can remain stable at 37 °C for 2 days). These precautions proved effective, as evidenced by the fact that at the time the last dose of each vial was administered the VVM stage was always reported to be acceptable. The VVMs were read and classified by the vaccinators, and not by a densitometer, which theoretically provides room for human error.