Maintaining 4 °C sounds doable with a good fridge and a data logging thermometer. −20 °C is more tricky—maybe use a home freezer (*** is specced at ≤ −18 °C) and add a data logger. If it then turns out that it can’t reach −20 °C, it might be possible to fix that by modding its internal thermostat somehow. Or have access to a lab freezer, or shell out the big bucks (four figures) to buy one.
As someone who has worked in the labs a long time, I wouldn’t worry about having to hit exactly −20 °C; that basically just means “freezer temperature”. Lab freezers don’t work any differently than home freezers as far as I can tell, although they do have certain safety features that a home freezer wouldn’t. But the temperature can still vary a few degrees up or down, and it shouldn’t affect your storage much. The (very) general rule of thumb is a difference of +/- 10 °C makes chemical reactions (such as peptide degradation) go 2x faster/slower. So even having to store in a fridge temporarily would only be ~4x faster than a freezer, still maybe good enough for one’s purposes.
The big difference comes for −20 °C vs −80 °C, since there you have a 2^6 or 64-fold rate difference. So something that can last for a month at −80 °C might degrade in half a day in a freezer. Hence the complex supply chains needed for such vaccines.
As someone who has worked in the labs a long time, I wouldn’t worry about having to hit exactly −20 °C; that basically just means “freezer temperature”. Lab freezers don’t work any differently than home freezers as far as I can tell, although they do have certain safety features that a home freezer wouldn’t. But the temperature can still vary a few degrees up or down, and it shouldn’t affect your storage much. The (very) general rule of thumb is a difference of +/- 10 °C makes chemical reactions (such as peptide degradation) go 2x faster/slower. So even having to store in a fridge temporarily would only be ~4x faster than a freezer, still maybe good enough for one’s purposes.
The big difference comes for −20 °C vs −80 °C, since there you have a 2^6 or 64-fold rate difference. So something that can last for a month at −80 °C might degrade in half a day in a freezer. Hence the complex supply chains needed for such vaccines.
Lab freezers have no defrost cycle. Home freezers often do, which prevents ice buildup but also means they don’t maintain temperature.
So that’s why those damn things were always so full of ice! Thankyou, I did not know this before.