According to the World Health Organization (WHO), more than one million infants and young children die every year from vaccine-preventable diseases such as pneumococcal disease and rotavirus diarrhoea. Polio is an example of an effective vaccination program. Indeed, the number of people diagnosed with polio has decreased by more than 99 percent since 1988, from approximately 350,000 cases to 1,352 reported cases in 2010. WHO states that the reduction is the result of the global effort to eradicate the disease; and only three countries (Afghanistan, Nigeria, and Pakistan), remain polio-endemic, compared to more than 125 countries in 1988.

Fig. 1 – The typical cool box and process that WHO prescribes to transport vaccines is prone to damaging the vaccines before they reach patients.

In addition to the rising costs of vaccines, the cost of transporting and sorting vaccines is a barrier to distribution. Many vaccines have to be kept at low temperatures to remain effective. Their temperature must remain between 2° and 8°C until they reach the patient to remain usable, according the U.S. Centers for Disease Control. This means that a “cold chain” of refrigerators and cold boxes has to be set up and rigorously maintained. The cold chain requires considerable logistical resources to keep vaccines cool in places where power supplies are unreliable and daily temperatures can soar to 45°C, which is particularly problematic in the remote and hard-to-reach areas where many people live.

For example, Ethiopia was faced with high attendant costs of a cold chain when it introduced the pentavalent vaccine, which offers protection against five childhood diseases, into its national immunization program in 2007. The country had to more than double its national capacity to refrigerate products to introduce this one vaccine.

The existing vaccine cool boxes have—as described by the WHO—four separate ice packs that first have to be put into a freezer to be frozen to to -18° or -20°C (See Figure 1).

Fig. 2 – Exploded 3D model of the basic design.

Then the packs are taken out to thaw for “conditioning” so that the vaccines aren’t killed by the freezing temperatures. Training is provided for this procedure but mistakes get made and ice packs lost. A lot of energy is wasted through the conditioning process as well. As much as 50 percent of all vaccines are spilled because of incorrect administration and improper storage, causing disruptions in the vaccine cold chain.

As part of his Master’s thesis, Product Developer Tibo Grandry consulted with Doctors Without Borders under academic promotorship of the Institute for Vaccines and Infectious Diseases. Grandry analyzed this cold chain at each of its steps and then looked for a suitable vaccine carrier solution that could work at the most extreme conditions and would decrease human error. Importantly, next to heat sensitivity, vaccines do not survive temperatures below 0°C. For usability, he determined that the new cool box should have only one ice pack and it should include a water buffer so that the ice pack wouldn’t have to be conditioned, thus eliminating the chance of vaccine damage.

Koen Beyers, CEO of Voxdale, a design, engineering and research agency based in Belgium, and CTO of Novosanis, a medical device company and spin-off from the University of Antwerp, acted as industrial promotor of Grandry to develop a prototype. At Voxdale, 3D thermal simulation with the computational fluid dynamics (CFD) software FloEFD from Mentor Graphics was used to analyze the efficacy of his design.

Creating the Models

They compared two different models of cool boxes and ran simulations to see which box design kept vaccines coolest for the longest amount of time. Figure 2 shows the 3D model.

Fig. 3 – a) The H500 design features the cooling pack in the center; b) The H501 design shows the cooling pack around the outside of the vaccines holders.

Figures 3a and b show the two different designs of coolers without the lid. The cooling pack was located in the middle for the H500 model, and the cooling pack was located on the outer edge for the H501 model. For both units, the volume of the cooling pack and cooling unit were the same, as were the simulation conditions.

Setting the Boundary

Conditions for Simulation The researchers chose to simulate a real time of three hours. Afterwards, they built a trend line in Microsoft Excel to extrapolate the results over a longer time. They also applied symmetry across the x and z axis to reduce the computing resources needed to run the simulation.

The researchers used the following materials in the simulations to represent the real product designs: Styrofoam for the cover and cooler, PVC for the cold pack and cooling unit, glass for the vaccine vials, and concrete for the ground that the box would be sitting on.

Table 1 - Temperature after three hours.

They also assumed the following initial temperatures in the simulations: 40°C for the cover, cooler, and soil; 5°C for the cooling unit and vaccines; and -20°C for the cold pack. The vaccine vials, cooling unit, and cooling pack were filled with water.

Comparing the Two Designs

Table 1 compares the average temperature of the vaccines and cooling pack after three hours for both designs. After three hours, the vaccines held at the lowest temperature simulation were in design H500. The difference is about 0.1 to 0.2°C. The temperature difference between the cold packs is quite large, at 1.6°C. This is because the cooling pack at H501 is on the outside.

Results for the H500 Design

Fig. 4 – For the H500 design: a) temperature distribution between 0°C and 40°C; b) the temperature distribution of between 0°C and 10°C; and c) temperature surface plot for the vaccines.

Figure 4a shows the temperature distribution between 0°C and 40°C. Figure 4b shows the temperature distribution of between 0°C and 10°C, which illustrates the difference in temperature in the water. That the upper vaccine has the highest temperature is a good result. Figure 4c is a surface plot for the vaccines, showing again that vaccine 1 has the highest temperature. Also you can see that the top of vaccine 1 is a lot warmer.

After about 6,000 seconds, the temperature rises linearly. During the first minutes (<500 seconds), the temperature of the vaccines rises slightly before cooling down (subsequently). After 3,000 seconds, the settled temperatures start to increase slowly.

Results for the H501 Design

Fig. 5 – For the H501 design: a) temperature distribution of between 0°C and 40°C; b) temperature distribution of between 0°C and 10°C; and c) temperature surface plot of the vaccines.

Figure 5a shows the temperature distribution of between 0°C and 40°C. Figure 5b shows the temperature distribution of between 0°C and 10°C, which again illustrates the difference in temperature in the water. For this design, vaccine 1 also has the highest temperature. Figure 5c is a surface plot of the vaccines. Again, vaccine 1 has the highest temperature, and the top is a lot warmer. After about 6,000 seconds, the temperature rises linearly. The temperature of the vaccines decreases evenly because the cooling pack sits against it, then the temperature starts to increase slowly after 1,000 seconds.

Conclusion

Fig. 6 – The COOL-VAX uses a single ice pack and storage compartments to keep vaccines from

The thermal simulations showed that the vaccines in the H500 vaccine carrier design would stay between 2°C and 8°C longer. The cooling pack and the cooling unit also stayed cooler for longer. In 2015, Grandry won the Belgian James Dyson Award for the device as a solution to a societal problem, and in 2014, the design won the award for packaging. The award aims to inspire and encourage the next generation of design engineers. The newest design of the product, called the COOL-VAX, is a carrier that allows for storage of vaccines for as long as 30 hours at 2 to 8°C using a central ice pack with a water buffer.

This article was written by Mike Gruetzmacher, a Technical Marketing Engineer with the Mentor Graphics Mechanical Analysis Division, based in Frankfurt, Germany. The company’s US headquarters is in Wilsonville, OR. For more information, Click Here .