Vaccine storage temperatures at different immunization storage levels and for different storage periods are summarized as follows:
OPV storage temperatures are -15 C to -25 C at the primary level for a maximum storage period of 6-12 months. However its storage temperatures at the health facility/service delivery levels are +2 C to +8 C for a maximum period of 1 month.
Freeze-dried/lyophilized vaccines (BCG, Measles, JE, Hib lyo, Meningitis, MR, MMR, YF, etc.) storage temperatures are +2 C to +8 C at the primary level for a maximum storage period of 6-12 months and at the health facility/service delivery level for a storage period of 1 month. If diluent is included in the vaccine packaging it should also be stored in the +2 C to +8 C cooler. If diluent is supplied separately, it can be stored outside the cold chain but must be cooled before use.
If there is a temporary shortage of storage space in the +2 C to +8 C cooler, these vaccines can stored in the -15 C to -25 C freezer. However, diluents should never be frozen.
Freeze-sensitive or other vaccines that do not belong to the above (TT, DPT, Penta, etc.) storage temperatures are +2 C to +8 C at all levels for a storage period of 6-12 months for the primary level and 1 month for the health facility/service delivery level.
As Michel had mentioned freezing is not damaging to any freeze dried/lyophilized vaccine including OPV. OPV can be safely frozen and unfrozen repeatedly. Freeze-dried/lyophilized vaccines can now be stored at +2 C to +8 C. But if -15 C to -25 C storage space is available these vaccines can be safely stored.
The risk of freeze-sensitive vaccines being frozen is high at the lower level, where all vaccines are stored in one refrigeration compartment. Freezing of these vaccines is also possible with the use of unconditioned frozen ice packs inside the passive containers during transport or outreach vaccination activities. It is therefore important that each health worker should be trained how to handle vaccines particularly the freeze-sensitive vaccines. The use of reliable and WHO PQS pre-qualified cold chain equipment should also be observed and practised by health officers in the procurement and replacement of cold chain equipment.
It is true that due to diminishing polio campaigns the storage space allocated for OPV is significant and can be used for storage of freeze-dried/lyophilized vaccines, particularly at the national and sub-national levels.
Another important factor in the calculation of storage capacity is the vaccine wastage multiplier. A high wastage multiplier will result in a request for more vaccines. These vaccines that were added due to a high wastage multiplier have to be stored in the cold chain. Therefore a higher vaccine wastage multiplier is translated into higher costs due to additional storage space requirement as well as due to increase in quantity of vaccines. Vaccine wastage must be recorded, monitored and reduced at each level of the cold chain system.
Alejo H. Bejemino
Independent Consultant
Cold Chain and Vaccine Management