Comparing Vaccine Fridges
We now monitor thousands of vaccine fridges and consequently we get calls from clients to discuss some of the issues they are having. And I would have to say that all vaccine fridges are not the same.
There are a number of features common to most (all?) vaccine fridges including:
- Fan forced air which ensures that there is a more even temperature distribution throughout the fridge. Much like a fan forced oven, except obviously cold.
- Computer controlled with the compressor turning on and off in a more controlled manner. A domestic fridge typically has a vague temperature indicator as to when the compressor will turn on and then turns off again after a set time. Vaccine fridges turn on at a set temperature and turn off again at a set temperature.
- External temperature display so that staff will always know the fridge is working correctly
- Alarms including an audible alarm so that if something goes wrong staff will be notified immediately.
And then there are features that are optional including:
- Glass doors which allow staff to find an item before opening the door, but at the cost of thermal insulation for when the power fails. They will heat up faster.
- Alarm dialler and other alarm features so that staff can be notified when not present
- Built in loggers or external loggers. We strongly recommend an independent logger but that’s not what this blog is about.
Which leaves the question Are all vaccine fridges the same?
And the simple answer is NO.
Here are two very simple, but very, very significant differences:
- The location of the temperature sensorIn a food or drinks fridge, the aim is to keep them cold. So the goal is to then find the warmest part of the fridge and ensure it is at the right temperature. The warmest part of the fridge would be the front (because it is exposed to air first when the door opens) and probably at the top (though front to back matters more than top to bottom). So fridge manufacturers placed the sensor at the front of the fridge.But vaccines are more sensitive to freezing than being warm and so the aim of a vaccine fridge is to ensure that the vaccines don’t freeze. But if the sensor is at the warmest part of the fridge then it has no true idea as to the temperature at the coldest part.In one recent incident, simply moving the sensor from the front of the fridge to halfway into the fridge made a huge difference to the performance. Let me be totally clear at this point – if you looked at the fridge temperature on the controller it looked no different. It thought it was doing exactly the same job and the results on the display were no different. BUT the temperature loggers that were placed in various locations throughout the fridge gave a very different picture of what was happening. The back of the fridge was no longer freezing and the front of the fridge was still at a good temperature.
- Exposure of the cooling plate
There are models that have the cooling plate exposed within the fridge and other models that will have a barrier between it and the contents of the fridge. If the fridge is working optimally this won’t make a difference. But if there is insufficient air-flow then an exposed cooling plate can potentially lead to freezing of the product closest to it.Which does lead onto the one factor that is within the owner’s control – the size of the fridge. If the fridge is too small then it will be over stocked. An over stocked fridge will block the air-flow. But being fan-forced is one of the critical features of a vaccine fridge. This then means that there will be hot and cold spots within the fridge.So I would throw in a third difference:
The rule is simple – the bigger the better. Of course there are issues in regards to limited space available and limited funds, but it should be the stock levels that dictate fridge size. Anything else and you are compromising. Keep in mind that a new vaccine on the market, or a flu outbreak and your stock levels will increase.