This Posting proposes the concept of a ‘Buffered Temperature Chain’ (BTC) instead of a ‘Controlled Temperature Chain’ (CTC). The BTC concept uses the Mean Kinetic Temperature (MKT) reading set to +27C to predict the effect of excursions of temperature on vaccine. The concept of MKT, though used by equipment test laboratories, remains complex to grasp by managers.
But my main issue with this proposal is that if we adjust our expectations a little, we may not need either CTC nor BTC in our armoury of tactics to take vaccine to the last 20% of children, most of whom live in areas of difficult access and other extreme conditions.
First, we can adjust the inference in the posting that CTC vaccines may be distributed out of the cold chain at any or all stages of distribution. We could be content with taking vaccines ‘beyond the reach of the cold chain’, assuming this practice is limited to the most remote and difficult destinations where the cold chain cannot reliably maintain recommended storage temperatures.
Second in our drive for equity, we can remind ourselves that our rationale does not only apply to individual vaccines used in Supplementary Immunization Activities (SIAs), but also to routine outreach services offering a range of vaccines. We would prefer to avoid the certification of specific, new vaccine products as CTC-qualified because distributing several versions of the same vaccines adds to complexity of distribution.
Finally, the accuracy of each VVM type (recently enhanced by a high temperature threshold indicator), that are matched to vaccine products has been extensively verified and an agreement to start using them was reached between WHO, UNICEF, manufacturers and regulators many years ago. On the understanding that vaccines are kept in the cold chain until used, in the event of a failure of cooling, they may be administered without a critical loss of potency if the VVM has not triggered. In other words, if a health worker walks to a remote outreach site with a vial of Tetanus vaccine – for example – he/she may administer the vaccine if the VVM has not triggered. The vaccine may be administered even if the icepacks melted some time ago and when the vaccine is at an ambient less than the threshold indicator.
Free of either the restrictions of pre-qualification required for CTC or the interpretation of MKT, we can already use vaccines ‘beyond the cold-chain’ . The immunisation manager has provided the maximum cold chain protection that is feasible in the circumstances, but will not be prevented from using the vaccine beyond the cold chain to the limits of the stability of the vaccine. This works for most vaccines except for lyophilized vaccines including measles that, once reconstituted must be kept cold.
John Lloyd,
Supply Chain Consultant, France