POST 00475E : PROTECTION OF MORE COLD-SENSITIVE VACCINES
Follow-up on Posts 00391E, 00400E, 00412E, 00419E and 00428E
16 July 2002
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It is a long time that we had a contribution on this topic of protection of
cold-sensitive vaccines. Elly Tumwine Rweizire (mailto:[log in to unmask])
country logistician at UNEPI (EPI Uganda) has some comments, operational
questions and an interesting suggestion.
As his contribution was shared with a few people, we already have a
reaction from Robert Davis (mailto:[log in to unmask]) from UNICEF/ESARO and
Ãœmit Kartoglu (mailto:[log in to unmask]) from WHO
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We have a problem of fuel and our cold chain is mostly dependant on
gas-operated fridges, which have relatively high operational costs. Do we
have standard acceptable walkable distance between the service delivery
point and the recipients? With sparse population distribution, the problem
we have is not the vaccine storage capacity, but icepack freezing to
support the outreach programmes. How far can we extent the freezing facilities?
Now that the freezing point of DPT-HepB+Hib has pressed a demand to relax
the cold chain temperature ranges from 0°C to + 8°C, with a shift to +2°C
to +8°C, what do you say about increasing the use of fast cold chain?
Before we get VVM on all other antigens, how safely can we relax our cold
chain system and preach use of chilled water bottles and not frozen
icepacks any more?
I was wondering whether you have considered construction of storage racks
that could be made with fridges to accommodate vaccine vials. These could
even be sized for vaccine carriers. They can be stacked in a refrigerator
or freezer. (Some thing similar to what laboratories use for keeping their
materials - reagents, specimens). If these were made of plastic, they would
solve our concern of avoiding direct vial contact with a frozen icepack
when used in vaccine carriers. The quantities of vaccine to health unit
become small and the packing boxes end in the districts and not beyond.
It is becoming difficult to ensure sustainable supply of cardboard or hard
papers at unit level to avoid this contact. While one suggests that the
icepacks should be left to melt first, there is a lot of relativity in
this. What would be the initial icepack temperature? How much time should
one allow for this ice pack to melt? If the ambient temperature is harsh,
what would be the effect on the other antigens that may remain at the end
of the session? What if the health worker has to stay overnight?
Elly
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EPI would definitely benefit from a low-tech technology to assure
noncontact between the more cold sensitive vaccines and the icepacks in the
vaccine carriers. I would suggest, however, that his ingenious idea of a
kind of plastic framework ("storage racks") to place vaccine vials in the
vaccine carrier at point of use be copied to the Far East low tech
manufacturers of vaccine carriers, to whom it could be a viable commercial
proposition.
Could someone with more artistic talent than the present writer make a
sketch of the framework so that Technet readers could picture what the
device would look like?
Bob
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Regarding melting of icepaks I would like to refer to TechNet postings
00391 and 00400. It is very difficult to give a length of time for
conditioning. Everything depends on the icepack temperature, ambient
temperature, number of icepacks you are conditioning. Recently visiting a
cold store in Tanzania, we took one icepack out of the freezer and placed
it on the table to time the process of conditioning. The icepack was at
minus 23° C, and the room temperature was 25° C. It took exactly 1 hour to
melt it down to zero degree with some liquid water inside and a big core of
ice in the middle.
The trick is to shake the icepack and hear the ice floating in it. This
means the icepack is ready to go into the cold box. Otherwise, temperature
is always below zero which increases the risk of freezing if used. I agree,
this is time consuming and would take longer time, say if you have to send
vaccines by 7 in the morning, when the ambient temperature will most likely
be lower than the one at which the test was made in Tanzania.
Ãœmit
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