If freeze alert (freeze indicator) is cross minimum one hour, can we suspect this T series vaccine is frozen and discard it, since it is difficult to confirm by doing shake test whether vaccine been frozen or not.
Dear Tshewang .
Thank you for raising this issue and apologies for the delay....
A freeze alert or electronic freeze indicator is a temperature monitoring device used to detect whether a vaccine has been exposed to sub-zero temperatures, typically below –0.5°C. These devices are commonly used in cold chain systems to protect freeze-sensitive vaccines like tetanus toxoid, DTP, and hepatitis B. The device is programmed to trigger an alarm if the temperature drops below a set threshold (usually –0.5°C) for a cumulative duration of 60 minutes or more. Once triggered, the indicator permanently displays an alarm status, even if the temperature returns to normal. They do not provide details about how far below freezing the temperature dropped or for how long beyond the threshold.
When interpreting the freeze alert, bear in mind that:
- A freeze alert means the vaccine may have been exposed to damaging conditions.
- For vaccines containing aluminum adjuvants (e.g., tetanus, DTP), freezing can cause irreversible damage to potency and safety.
We know that tetanus-containing vaccines contain adjuvant that is sensitive to freezing. Although the freeze indicator is showing a freeze alert, the WHO recommends performing a shake test to confirm whether the vaccine has indeed been frozen. The reason for this is we need to be very sure that the vaccine has been damaged and must be discarded; and rule out the possibility of a device malfunction (which remains a possibility). We encourage this to avoid unnecessary disposing vaccine that is still potent and effective. The shake test result will also provide an affirmative justification why the vaccine has to be disposed. Discarding vaccine, especially in large volume will have serious consequences, such as stock out, high wastage, missed opportunity and potential public loss of trust. If the shake test confirms freezing damage, the vaccine must be discarded and this has to be documented for audit purposes as well. If the test is inconclusive or cannot be performed the vaccine should be quarantined and assessed according to national SOPs.
We understand that performing a shake test maybe challenging. However, the procedures are simple….just make sure the observation is done in a well-lighted area, preferably where there is natural light.
Here is a video on how to perform the shake test. To prepare the control vial, you may take one or two vials from the suspected batch and deliberately freeze them. It is not necessary to prepare a control vial from a known good batch.
https://youtu.be/h1PRg4Mew8M?si=D07kGn3nvwuZ9srW
Let us know if you have other questions or concerns.
Best,
Maricel on behalf of the VSCL Team/WHO HQ
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