Many thanks to Michel Zaffran, EPI Coordinator, WHO, for this response.
Freezing is not damaging to any lyophilized /freeze dried vaccines such as BCG, Measles, MR, MMR, yellow fever , Men A, JE, etc… this applies to OPV and Rotavirus as well. The thermostability profile of vaccines can be found at:
http://www.who.int/vaccines-documents/DocsPDF06/847.pdf. PATH has also recently published vaccine stability data which can be located at:
Vaccine Resource Library
For OPV, studies conducted by WHO and the UK NIBSC laboratories in the mid-1990s have demonstrated that up to 10 freeze/thaw cycles do not affect the potency of the vaccines. So freezing of these vaccines should not prevent use of the vaccine.
A Freeze VVM, if it ever becomes available at an affordable price, would not work any differently than a fridge-tag or a freeze-tag. It would activate at a pre-set temperature and it would not necessarily indicate true damage by freezing but rather exposure to the above pre-defined sub-zero temperature.
The best guidance therefore that can be provided as of today is:
1) to avoid freezing and exposure to sub-zero temperatures through appropriate monitoring of the cold chain and proper vaccine management practices;
2) in case of exposure to sub-zero temperatures and in case freezing is suspected and the shake test cannot be applied, then the vaccine should not be used and the matter referred to higher levels. If significant quantities of vaccines are at stake, then a specific investigation could be carried out.