A study into Tunisia’s transition to a controlled temperature chain for the cold storage and transport of vaccines. Since the inception of immunization programs, the cold chain has been the optimal choice for vaccine storage and delivery. Through time, the process of maintaining the temperature between 2℃ and 8℃ (35°F to 46°F) proved to be difficult. During transport, vaccines must be placed in carriers and cold boxes with cooling packs and temperature sensors. In storage, freezers and refrigerators housing the vaccines must be kept connected to electricity for the duration of immunization campaigns. In short, adhering to cold chain requirements is expensive and energy-consuming.   

The cold chain is also prone to many problems. The World Health Organization (WHO) estimates that about 50% of the world’s vaccines are wasted every year due to cold chain errors, aside from other logistics issues. 

To prevent such yearly misfortune, alternative approaches to the vaccine supply chain are being developed. One of them is the controlled temperature chain (CTC) — a process of allowing vaccines to be kept at temperatures outside of the cold chain range of 2℃ to 8℃ (35°F to 46°F). Vaccines can still be potent as long as the temperature excursion does not exceed 40°C (104°F) and lasts for only a few days prior to administration. 

The problem is that CTC is fairly new. In fact, there’s only one vaccine—the MenAfriVac®—that is WHO pre-qualified to be stored at controlled room temperature (CRT) conditions. If improved, CTC can save thousands of vaccines and millions of lives. The world will benefit from the development of CTC procedures. Hence, manufacturers in Europe and the United States test and label one-third of their medicines for CRT storage.

A Developing Country’s Approach to CTC

PATH collaborated with WHO to form a project called Optimized. Together they conducted a study in Tunisia about the possibility of storing CRT-labeled vaccines. It involved the assessment of their rooms and their possible enhancement to be effective controlled room temperature (CRT) storage areas. 

The goal of the study was to assess the least cost, most energy-efficient solutions to control the temperature of Tunisia’s storage rooms. 

The project focused on three steps: 

1. Assessment of storage parameters. 

a. Packed volume of medicines for CRT storage. 

b. Assessment of monthly ambient temperature profiles. 

c. Energy audit of the regional store and three district stores. 

2. Engineering assessment of five potential alternative solutions

a. Natural or passive conditioning. 

b. Part-time space conditioning. 

c. Full-time space conditioning. 

d. Specialized space conditioning and humidity control. 

e. Dedicated conditioned space within a room, or a dedicated storage cabinet (i.e., kit cool room with heater). 

3. Analysis and synthesis of workable solutions.

Assessment of storage parameters

The team first measured the packed volume of medicines for CRT storage by measuring the CRT labeled medicines used in the region for three months.

Here is the result: 

In assessing the monthly ambient temperature of the Kasserine Region, a climatic assessment was made. The Kasserine climate requires both heating and cooling, but cooling is the most pressing need. 

Here are the monthly ambient temperatures of Kasserine: 

In each pharmaceutical store, an energy audit was conducted. The audit was limited to the storerooms. The study focused on energy-consuming aspects of the stores: heating, ventilating and cooling (HVAC) systems, building envelope construction, and refrigeration appliances.

There are only five proposed solutions to improving CRT storage in Kasserine. Project Optimized hired consultants to do a feasibility study of the five solutions, and assess their reasonability, cost, and efficiency. Here are the results of the consultants’ study: 

Among the five solutions, numbers 3, 4, and 5 were the most technically feasible. The table below provides the data showing why the “room within a room” and the “kit cool room” solutions are both less costly to install and to run than other solutions. United Nations Children’s Fund supplier Porkka, Finland quoted the installation costs. 

Like most stores in other countries, existing government buildings in Kasserine’s regional and district stores are not designed for CRT storing of medicines and vaccines. The only way they could be suitable for CRT storage is through retrofitting and adding of equipment. The existing space-conditioning in their stores cannot adhere to CRT requirements. They are only used for human comfort during extreme weather conditions. 

Operating a full space conditioning is prohibitively expensive as this study shows. A lot of buildings in Kasserine are not energy efficient and using them for CRT storage will not be economically feasible. 

Retrofitting buildings to improve energy is costly, complex, and disruptive to ongoing programs. Older buildings will require added insulation, reduced air infiltration, and control of both internal and external heat gains. Because the volume of CRT storage required will usually be less than the volume of the building, retrofitting the entire building is not economical. That’s why it is advised to establish new warehouses or to find newly established warehouses that are energy efficient and can accommodate the volume of medicines, vaccines, and dry stocks. 

In building new warehouses, zero-energy designs can help achieve a CRT condition. Zero-energy designed buildings already exist and are increasing in number. The chance to adapt these designs to new buildings will make CRT storing of medicines and vaccines energy-efficient. 

CRT equipment, being fairly new in the market, is currently expensive. When supplies expand in response to growing demand, price is expected to fall. Retrofitting is also expensive generally, but there are inexpensive ways such as low-cost wall and ceiling insulation and cheap air ceiling techniques that can be employed. 

CRT-labeled or thermostable vaccines can change the landscape of vaccine storage and distribution. For now, most vaccines are still required to reside in the cold chain. In the future, when most of them can withstand an ambient temperature of up to 30℃ (104°F), the percentage of potency loss will decline. This will benefit all countries, especially resource-poor locations where electricity is unreliable and they lack the capability to provide expensive storage for their immunization programs.


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