POST 00407E : FREEZING AND VACCINE EFFICACY

POST 00407E : FREEZING AND VACCINE EFFICACY Follow-up to Posts 00402E and 00406E 9 January 2002 _________________________________________ Fred Binka from Ghana commented that we have to take advantage of special circumstances to accumulate more information on this subject. However for most people in Africa, he says, the major problem is the cold chain. Any one working under these conditions will advice we spend the resources available to do away with the cold chain. He said that we are certainly looking forward to a cold chain free vaccine delivery system in the near future. John Lloyd believes that the question we face is the still the same one - is there enough evidence that freezing fundamentally affects potency of some liquid vaccines, not just homogeneity, to warrant a managerial decision to assure that ALL vulnerable liquid vaccines should be protected from freezing? He believes the answer should be yes, as it was twenty years ago. The evidence, however is patchy, contradictory and very old and he is sure that work is needed to document the effects of freezing for current commercial vaccines. The cost impact of saying 'yes' now is mainly determined by the decision to switch from kerosene to solar refrigeration where there is no electricity - which could be costly in the short term. Otherwise, the cost impact is probably slight. The reformulation of existing vaccines, particularly the traditional low cost vaccines, to reduce the risk of freezing is a large, complex operation and highly unlikely to happen. The formulation of new vaccines on the other hand, should be guided to eliminate the effect of freezing - not likely to be costly if upstream. Our efforts to remove ice from the transport system, to improve vaccine handling and to remove vaccine from the cold chain where possible should reduce the risk of freezing at little extra financial cost. These efforts are needed in any case. Freeze protection in cold boxes, when the ambient is sub-zero, can only be achieved by water/eutectic packs and good insulation - no extra cost. With the lab data already in WHO, we can calculate the freeze protection of all current PIS cold boxes....a small test can confirm the calculation...and the performances published in the PIS. Freeze protection in refrigerators, when the ambient is sub-zero, is easily achievable where there is electricity with heaters and fans on special 'sub-zero' models - yes extra cost but no big deal. Models need to be identified though and put in PIS. The question remains for the kerosene refrigerators operating without a thermostat and/or means of heating. Either a thermostat should be developed (difficult) or we should stop using kerosene as a policy. That means more solar equipment. So, in conclusion, John says : “lets say yes to avoiding freezing and - lets obtain data on the effect of freezing current vaccine products that are vulnerable - require that freezing not affect newly formulated vaccines - continue to test out of the cold chain and cool transportation - calculate and lab-check the freeze protection obtainable with existing PIS products - seek refrigerator models with heaters/fans for areas with sub-zero ambient temps - or - - require that all vaccine refrigerators have capability to protect against freezing and - consider a future policy to outlaw kerosene refrigerators without thermostats used for vaccine storage.â€