Preventing vaccine freezing during transportation in Immunization Programs throughout the world remains the challenging task. Will reinventing the icepack (wheel) make a difference?
Modified frozen Icepacks compared with conventional (not modified) frozen icepacks use in cold boxes in the presented study.
Two insulated polyurethane transport boxes used for international vaccine shipping, 62 icepacks (0.4 Liter), and temperature data logger.
Modification of study icepacks: Two conventional icepacks connected with plastic tube. First icepack frozen and second icepack empty, kept at the room temperature.
In each box 18 frozen icepacks placed. Initial temperature of icepacks (-5°C). Three sensors used in each box: one placed at the bottom of box, second on icepacks, third on top level of box. Ambient temperature recorded with additional sensor.
Ambient temperatures were about (~28 °C) throughout the study.
Surface temperatures of conventional (not modified) icepacks remained below zero °C about 75 minutes.
Surface temperature of modified icepacks very rapidly stabilized at (+1 °C) in first 10 minutes.
Temperatures at bottom and the top of both boxes reached recommended by WHO (+2 °C - +8 °C) range in the box 2 (study) in 50 minutes and in the box 1 (control) in 65 minutes.
Interesting finding is what in cold box 1 (control) temperatures at the bottom of cold box during first 30 min were close or below zero °C, when in cold box 2 (study) temperatures at the bottom of cold box did not reached subzero temperatures. After initial rapid descend from ambient temperature level in first 30 min, temperatures at the bottom of cold box 2 (with modified icepacks) stabilized at 6°C.
At ambient temperatures (~ 28 °C), study showed that, with the use of modified frozen icepacks, temperatures inside the cold box remained above 0 °C, potentially preventing vaccine freezing. Subzero temperatures documented inside control cold box (box 1), with use of conventional (not modified) frozen icepacks.
Further exploration needed to identify possible icepack modifications and confirm study results in other test centers and in the field.
[color=#0033ff]To be continued…[/color]
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Dear Andrey and Larry thank you very much for your excellent questions
1. Test repeated 3 times.
2. No dummy or real vaccines used.
3. Preparation of modified icepacks takes between 10-15 minutes.
4. Risk of non-proper preparation of modified icepacks always present as it done by humans, although freezing risk minimized by both modification and “involuntary” icepacks conditioning
It would be great if you could repeat test and share your experience
It's an interesting study, but could you please answer:
1. How many times (repeats) you perform this test?
2. Is test with "sample load" was done?
3. How long it takes to prepare modifided icepacks?
4. Is it any risk of non-proper preparation of modified icepacks?