Thursday, 02 July 2015
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Hi all,

I am quite new to the CTC adventure.

After reading the second draft of the WHO CTC guideline, now ECTC (I also wen through the first version and the discussion in Langen and Ottawa), several questions came to my mind, and I would be extremely grateful if some of the forum members can help me out with them

1- Now that the rigid time& temperature conditions of the CTC are only one of the extended temperature conditions eligible for re-labelling, can we assume that the stability studies conducted by the manufacturers when deciding the most appropriate VVM type to reflect their product decay (at 5, 25 and 37°C), can be used for a re-labeling purpose with 37°C as a max. threshold temperature?

2- For those of you who followed the CTC initiative from the beginning, what was the scientific ground to choose 40°C as a threshold, rather than 42, 45 or 37 for that matter? In many countries where MSF intervenes & where a CTC approach can have a great impact, ambient temperatures exceed 40°C during the hot season and can be below 37°C during the cold season.

Thank you beforehand for your answers and thoughts.


Pharmacist, MSF

8 years ago

Dear Alain:

As noted, the stability studies done by manufacturers are only one of the elements that need to be considered when exploring the possibility of a product being suitable for use in a CTC. The studies conducted to assign a VVM are useful for giving an indication of CTC suitability but on their own are not sufficient for relabeling—hence the need for the full guidelines on licensing vaccines for use in a CTC which are, as noted, currently under finalization with WHO’s Essential Medicines Programme. These will go to WHO’s Expert Committee on Biological Standardization for endorsement in October.

The decision of what temperature threshold to choose is not easy. Ideally there would of course be no upper limit. But in reality, vaccines are biological products and exposure to higher temperature does have an impact on their potency. The higher the temperature threshold chosen, the shorter the duration of time that a product can be kept at that temperature. Choosing a limit higher than 40C means the time available for use in a CTC drops dramatically and no longer becomes programmatically feasible. Lowering the threshold to 37C while giving us more days, severely limits the places where CTC can be used given that temperatures are regularly above 37C but below 40C throughout the year. Several temperature monitoring studies done by placing temperature loggers in vaccine carriers during outreach activities showed that, during standard activities, temperatures rarely reached 40C, while they did often surpass 37C. Therefore the ability of a vaccine to be used at temperatures of up to 40C for a period not shorter than 3 days was set as the minimum threshold for CTC licensure.

Diana Chang Blanc

WHO EPI Geneva

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