Most of the countries now have improved immunization coverages and reach more children with vaccination, but we still need to monitor the potency of vaccines that are given on top of the high coverages we have achieved in many countries.
One of the biggest challenges when we talk about vaccine potency is the storage condition and to be more specific “the storage temperature”. Most of the vaccines are either heat or freeze sensitive and we need to monitor the storage temperatures more closely so that we can have potent vaccines given to the children and hence achieve higher coverages with potent vaccines.
There are several technologies that are currently applied in monitoring temperature of cold chain eg. VVM, Fridge and Freeze Tags, different types of RTM devices are now coming up. All this aimed at ensuring vaccines are stored in correct temperature to maintain potency. But, with all those devices the human component is not replaced and we still need someone to act upon the alarms or signs from those devices to ensure correct temperature are maintained all the time in vaccine cold chain.
Based on the field experiences (9+ years) in immunization program, I am still not sure if the closed vial wastage due to freezing for freeze sensitive vaccines reflect the reality. That means, I doubt there are many children who are probably receive vaccines which have been exposed to freezing. We are very good in monitoring heat exposure because of VVM and we have observed closed vial wastage due to VVM change reported but freezing exposure is very difficult to monitor especially in the scenario when the facility does not use temperature monitoring devices that gives freezing alarms. The actions taken following low temperature excursion at the facility level makes me more worried and I feel there is a need of looking at this issue with an additional eye.
Currently, many countries are getting into the new technologies of temperature monitoring but in some countries the coverage is still low. We may be proud of our improvement in the global immunization coverages but may be many of those kids are vaccinated with vaccines that are exposed to freezing. Being proud of the improvement of the global immunization coverages is good but we need to be confident that we have improved coverages with potent vaccines that are kept in recommended storage conditions. Use of modern technologies and innovations around temperature monitoring while working to improve immunization coverages is very important and this should off-course go hand in hand with behavior change on acting upon temperature excursion among those who are involved in vaccine cold chain.