Freeze sensitive vaccines, what can be done to protect and monitor them from freezing conditions during storage and transportation? There are many vaccines that are sensitive to temperature changes, and it is commonly known they should be kept refrigerated between 2°C to 8°C. (35°F to 46°F) However, sometimes in an effort to maintain low temperatures, accidental freezing can occur. This can be equally, if not more damaging in some cases than short periods of exposure to temperatures over 8°C (46°F).
There are several vaccines that are sensitive to freezing temperatures. These include some common vaccines such as HepA, HepB and HPV. These should never be frozen, any exposure to sub-zero temperatures can irrecoverably damage the vaccine, striking at its efficacy to immunize the recipient.
Freeze Exposure Monitoring Strategies
There are several strategies that can be used to monitor your vaccine storage temperatures, and check for exposure to freezing temperatures. The 3M FreezeWatch™
There are several strategies that can be used to monitor your vaccine storage temperatures, and check for exposure to freezing temperatures.
3M Freeze Watch™
The Freeze Watch™ is a simple and inexpensive way of checking if the environment inside your refrigerator or cooler has been exposed to sub-zero temperatures. It has a special liquid inside a small glass ampoule which will break at a given temperature. They are available in different temperature ranges either -4°C (25°F) or 0°C (32°F). If the liquid inside freezes, the ampoule will break and the paper behind will be stained with the liquid. They can be placed inside temperature-sensitive shipments to check the cold chain temperature stability during transit
How to Use 3M Freeze Watch™ Indicators:
- Attach the Freeze Watch™ indicator using the pressure-sensitive adhesive on the back. Peel the release liner off the back and adhere the indicator to a clean, dry surface.
- Before reading, the indicator should be in an area above freezing temperature for at least fifteen minutes.
- To detect if the product has been exposed to freezing temperatures, observe the Freeze Watch™ indicator. If the indicator paper is stained with colour, your product has been exposed.
- If the indicator paper shows no colour indication, remove the indicator from the surface to which it is attached. Vigorously tap the bottom edge of the indicator three times on a hard surface. If the paper becomes stained, your product was exposed to freezing temperatures. Tapping will not cause colour staining in an unexposed indicator.
Another technology that has the same function as the 3M Freeze Watch™ is the Freeze-Tag from Berlinger & Co, Switzerland. This is a compact, Lithium-Ion powered device. It complies with IATA guidelines and rules regarding Lithium-Ion batteries. The sensor is NIST calibrated and comes in three different activation temperatures. Below 0°C (32°F) for 60 minutes, below 0°C (32°F) for 10 minutes and -0.5°C (31.1°F) for 60 minutes.
The Freeze-Tag is easy to use with a clear LCD display indicator of a “check” or “cross” to show if the tag has been activated. They are single use and cannot be re-set after exposure.
The shake test can be used on adsorbed vaccines such as DTP, DT, Td, TT or Hepatitis B. After being frozen these vaccines tend to no longer have a cloudy appearance, instead after shaking flakes will form and sink to the bottom of the vial.
- Prepare a frozen control sample. The vial should be from the same batch as you suspect having been compromised. freeze the vial until the contents are frozen solid, which would be a minimum of 10 hours at -10°C (14°F). Make sure that this control sample is clearly marked.
- Select a test sample. This vial should come from the batch you suspect has been frozen.
- Shake the control and the test samples. Hold both vials together and shake vigorously for 10-15 seconds.
- Allow to rest. Place both vials on a table to settle and do not move them further.
- Compare vials. Hold both to the light and compare the sedimentation rates. If the test sample shows a much slower rate than the control sample then it likely not to have been frozen.
- Segreagate and dispose. Immediately segregate and label the compromised vials and notify your superior. They should be disposed of correctly.
How to load a vaccine refrigerator
In order to protect vaccines from incorrect temperature exposure, otherwise known as a temperature excursion, there are guidelines on how you should load a vaccine refrigerator.
- Only store vaccines in the refrigerator, no other medications or food and beverages should be present
- Do not put vaccines on the door shelves, the temperature is not stable and fluctuates quickly when the door is opened
- Do not keep expired or temperature compromised vaccines in the refrigerator
- Refrain from opening the refrigerator door often
- Arrange vaccine boxes so air can circulate around them
- Do not place vaccines nearby sides, bottom or top of the refrigerator where they are more prone to freezing
- avoid overstocking the refrigerator
- Arrange vials with vaccines that expire soonest at the front and any with Vaccine Vial Monitors (VVM) that show temperature exposure at the front for first use.
- Keep ice packs filled with water in the refrigerator door compartment and bottom shelf
A vaccine refrigerator will have two compartments. A refrigerator compartment that is maintained between 2°C to 8°C (35°F to 46°F) which is for storage of vaccines. The freezer compartment is maintained between -5°C to -15°C (23°F to 5°F) and is used for storage of ice packs. The below diagram illustrates the best practices to use when loading a refrigerator.