POST 00407E : FREEZING AND VACCINE EFFICACY
Follow-up to Posts 00402E and 00406E
9 January 2002
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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€
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