Vaccines can tolerate temperatures above 8 deg C however temperatures below 0 deg C will freeze a vaccine and it will lose it’s efficacy. At temperatures above 8 deg C the life of a vaccine will be lowered but the exposure will not be catastrophic. For the most sensitive vaccine, VVM II, the life of the vaccine will decrease from 104 days to 99 days when exposed to 20 deg C conditions for one day. For a VVM7 vaccine exposed to the same one day temperature excursion the life of the vaccine will decrease from 650 days to 643 days. As Umit points out in a recent post [High Temperature Freezers], it is sometimes logistically difficult to get ice packs conditioned for an early morning departure. SDD freezers do not cool at night and as a consequence in the morning the ice packs are conditioned or close to being conditioned. Similarly, if an ice pack carrier is loaded with ice packs the night before a trip the ice packs will be conditioned or near conditioned the next morning. If the ice packs are not completely conditioned, they could be placed in the carrier earlier in the day to increase conditioning time.
If a reader is involved in vaccine distribution this technique can easily be tested. In the afternoon, cold ice packs would be placed in a carrier along with a thermometer. The next morning the temperature of the carrier would be recorded and the ice packs examined. Water in the ice packs indicate that the ice packs are conditioned. It is most critical that the ice packs closest to the vaccines are fully conditioned. If the ice packs are not conditioned, repeat the experiment with the ice packs placed in the carrier earlier in the day. If, for example, the ice packs are conditioned 5 extra hours over the minimum conditioning time to reach 0 deg C, the consequence would be minimal. The length of time acceptable temperatures are maintained would be only reduced by 5 hours. Using “Crowed Testing” the effectiveness of this technique could be easily determined.
If you are involved in the distribution of vaccines, I would appreciate your help in evaluating this method. Please send your answers to the following questions to Tech Net
- Model of carrier
- Number and size of packs in carrier
- Ice pack freezer temperature
- Number of hours in carrier over night
- Average ambient night time temperature
- Temperature of the carrier in the morning
- Is there water in the ice packs?
- Do you estimate more or less time is needed for conditioning?