This is the third posting I have made on in-country transport of vaccine. The first two postings opened issues for discussion on vaccine storage temperatures and on optimizing inter-store transfers. This posting focuses on transport for outreach immunization in the context of a passive-cooled supply chain. I invite you to start a dialogue on all three facets of vaccine transport that we could use to review policy and propose revisions or next steps. Outreach services are mobile, provided at a distance from fixed health facilities by walking, cycling, motor-cycling, driving, boating and even flying to a temporary service delivery posts.
Currently, vaccines are transported in carriers and boxes frozen, or at +2C to +8C depending on the type. Diluents must be cool at the moment of reconstitution and they often enter the cold chain at the health centre because this is typically the last stage where active refrigeration is provided. The dis-advantages of the current system is that refrigerators require maintenance, repairs, energy and require scarce electrical skills to install and maintain. They also have performance limits, usually able to operate up to +43C. These characteristics suit many situations but the more remote rural areas, especially those with extreme temperatures are a major challenge. It is precisely these areas where the population is hard to reach and immunization and other health services have not been provided.
Technology to help extend immunization to these remaining populations is arguably the most challenging target of the next decade. With this in mind, consider a cold-chain based on passive cooling at the level of service delivery, that does not require electrical maintenance, that has no limits to ambient temperature and which is robust enough to resist hard wear for decades. Such a passive system might rely on a ‘hub’, a fixed district facility where cold-packs are ‘charged’ to cool highly insulated containers that are used to store vaccines at the health centre for a month before they need a re-charge. Depending on the situation the containers may be transported to outreach sites by a vehicle, or the vaccine for outreach is transferred to a smaller high performance carrier cooled by designated icepacks drawn from the container. Diluents will be cooled on site at the time of the immunization session by an innovative portable device and the conditions of storage will be remotely monitored.
Note: S.I.A = Special Immunization Activity; ie. Elective campaigns for polio, MNT, measles and outbreak control
The figure illustrates one scenario for outreach to show equipment needs (new equipment starred). Most of the equipment listed is new and either recently available via WHO/PQS or will be available soon. The system is still being field tested and expected to be available at competitive whole-life costs to conventional equipment while being able to operate more reliably in more extreme conditions.
In the spirit of transparency, if you are engaged in this new development please share news of progress with Technet and if you have not already given your views, we would welcome to see them presented here for the discussion.
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REPLY TO: Gopal NATADUR, CHAI DOUBTS REGARDING PASSIVE-COOLED SUPPLY CHAIN
Gopal, good to have your response via IAPHL - it's the first I have received!
Following your headers, I am delighted to debate this with you because it coincides with a number of changes in the vaccine distribution paradigm that may change in the near future:
EXPENSIVE
We do need a full costing on the passive model, I agree. But we should take into account the following:
a) SDD refrigerators have not demonstrated a target 'time-between-repairs' of >36 months that was our expectation for solar-battery systems at the start of the millenium. Unless we succeed to make SDDs with near 'whole-life' reliability, the cost of technician repair visits to remote areas will be prohibitive. Transport costs for around 7 kgs of icepacks per month should not exceed the vaccine transportation costs per month. The procurement cost of the 30-day cooler is not known but we are counting on a financing subsidy to offset any differences.
UNRELIABLE
Transport availability and reliability was, I believe, the main reason for the failure of UNICEF's attempt to run a weekly passive-cooled 'last-mile' in Nigeria in the early '90s, you are right. But the critical success factor for the entire distribution system will be a reliable available transport, whether shared or dedicated. I believe wa can achieve this by:
a) adopting a policy of 100% vaccine deliveries, not collections. This way, the logistics management is controlled from the District for the periphery and control can be more easily achieved;
b) If vehicles are shared at the district for allocation to tasks at the periphery, there has to be a single logistics/transport manager to programme the allocation for all public health initiatives and to assure preventive maintenance. This we might call the 'Common Operating Platform' for Universal Access to services.
DIFFICULT TO SCALE UP
We (PATH) researched this in the logiistics 'Streamlining' project in Indonesia in 2003-2005. The 'Moving Warehouse' system that we used to unite supervision, vaccine supply and sharps waste collection was a 100% delivery system. We inserted this system in districts of Yogjakarta and it worked well for a limited radius around the supply stores. The most remote areas required such a heavy transport burden and so much supervisor time that the system worked only with a 3-month supply interval. Centralizing the transport improves the quality of control, vaccine handling procedures and budgeting.
And there is the 'show-stopper' question with passive systems: can the current 1-month supply interval (vaccine supply and re-icing) be efficiently maintained at an affordable cost? That, I hope, is the objective of the 'passive-cooling' champion's objectives for field trials. Let's Skype!
Hi John,
Your post was informative regarding the implementation of a passive-cooled cold chain to reach remaining populations underserved by the traditional cold chain. You mentioned that SDD refrigerators have not demonstrated target times between repairs greater then 36 months. What has been the time between repairs for SDD refrigerators?
I was wondering if you have seen our post on MKT thermometers. An MKT thermometer would measure the thermal stress on a vaccine in much the same way that a VVM measures the temperature stress.
http://www.technet-21.org/forum/cold-chain-equipment/8587-vvm-mkt-equivalent-and-complementary-concepts
The MKT thermometer could be reset at the beginning of a trip and the MKT temperature at the arrival point would tell you the percent loss of life due to temperature excursions.
A MKT thermometer would be an asset to the new passive-cooled cold chain or it could be used with conventional ice pack carriers.
Sincerely,
Larry Schlussler, Ph.D.
Hi John,
Another point to consider is that in remote clinics requiring both ice packs for outreach programs, and refrigeration for vaccines, a 30 day passive refrigerator could be used in conjunction with a SDD ice pack freezer. For several days each month the freezer could be used for freezing ice packs for the passive refrigerator and for the rest of the month the freezer would be available for freezing ice packs for outreach programs. Usually a freezer, as the one produced by Sunfrost, can be powered by a single module. This would result in a relatively simple system for both refrigeration and ice pack freezing. Typical SDD refrigerator/ice pack freezers require a much larger array and two separate cooling systems.
This scenario would also eliminate the difficulty pointed out by Gopal; transportation of ice packs from a central facility.
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