Evaluating The Sure Chill Passive Vaccine Storage Device

Published by admin on

vaccines and refrigerator

Getting life science products to remote locations in various countries is a huge challenge. Some of these areas do not a reliable power source where vaccine freezers need to be plugged in. Vaccine vials should be kept at precise temperatures to be effective. Too hot or too cold affects the potency. That is a huge problem for the cold chain provider.

There are more than 23 million children who are not receiving routine immunizations annually and more than 1.5 million children under the age of five are dying each year from vaccine-preventable diseases, like tuberculosis. Part of the blame is attributed to limitations in the temperature-controlled cold chain that is needed to prevent vaccines from spoiling. This cold chain is well placed in various places in the world, but poor infrastructure and intermittent power prevent vaccines from reaching many developing countries. The Passive Vaccine Storage Device (PVSD) might be the solution all cold chain providers are looking for. This is designed to keep life-saving vaccines at appropriate temperatures for a month or more with repeat vaccine retrievals and eliminate the need for electricity.

Vaccines are only as good as the cold chain they are relying on, which is why Sure Chill has reinvented. About 75-100% of vaccines are subject to freezing temperatures at some point during the cold chain, which can destroy their efficacy.

To face the challenge, Sure Chill Company, a Welsh firm is working on a cooler that can keep its contents at low temperatures even without power. The company invented the device that will be able to keep vaccines cold for more than 35 days without power.

By offering an entirely freeze-free solution, Sure Chill uses chilled water packs, which are cooled in the very same refrigerators the vaccines are stored.

The company’s combined fridge freezer keeps vaccines perfectly cool in the absence of any power for days, and even weeks. The freezing of up to 24 ice packs can be used in portable vaccine carriers, the perfect device to finalize the ‘last mile’ vaccinations and outreach programs.

Using patented Sure Chill technology, the Passive Vaccine Cooler keeps vaccines perfectly cool for up to 35 days with no power and absolutely no risk of freezing.

sure chill cooling
surechill portable carrier

The Sure Chill technology works by using a unique property of water to provide 4°C (39.2°F) cooling. While the pre-frozen ice packs provide the cooling energy, Sure Chill ensures that vaccines are never frozen and always safely stored between 2 – 8°C (35.6 – 46.4 °F). In case the power is cut off, the liquid water will heat up, but the ice will start to melt, creating a cycle that will keep the water at that same temperature level for an extended period of time.

Sure Chill refrigerators regulate the internal temperature and protect vaccine vials from ice, to freezing while keeping the vaccines at the appropriately cold temperature so they can be delivered at the working condition to children and adults throughout the necessary regions. It works by surrounding the vaccine vials with cold water.

The technology uses the physics of water to store energy. When turned on, the water within the Sure Chill system cools and forms ice in a reservoir adjacent to the refrigerator compartment. This leaves only water of 4°C (39.2°F) cooling the chamber, suited for storing vaccines. If the supply is interrupted, the refrigerator will still continue to operate effectively until the ice stored has completely melted.

The refrigerator can provide stable temperatures for extended periods in unstable power conditions. This can eliminate the need for backup generators for refrigeration. The holdover time of the technology is ten days and 9 hours at 43°C (109.4°F) ambient conditions.  Once properly cooled, the refrigerator can still function even in a complete absence of power for ten days while still maintaining temperatures in the vaccine compartment below 10°C (50°F).

sure chill arrived in rural area
Churchill refrigerators delivered in Kenya

In faraway locations, which have high ambient temperatures and where there is no steady power, it is a big problem to keep lifesaving vaccines at a safe temperature for a sufficient length of time. It is important that sufficient vaccine quantities be kept at the prescribed temperatures. If the vaccines freeze or get too warm, they can lose potency and may not cure the patients, who are infants and young children, from the disease.

The Importance of the Sure Chill Technology

The Sure Chill LTPD was tested in Senegal as a stationary cold box. The performance of the device was evaluated in simulated use conditions in which the vaccine storage was opened once per day for five minutes. Availability of frozen ice packs was supported by cold chain staff at the district vaccine store (DVS) in accordance with Sure Chill’s coolant recharging instructions, including ensuring necessary monthly replenishment of ice packs.

Power problems have always been a perennial problem throughout the developing world that including countries like Senegal. The standard procedure here in the cold chain is to rely on diesel generators to back up unreliable grid electricity. But generators are costly, difficult to maintain, create noise and air pollution, and are subject to fuel shortages.

This field test of the Sure Chill LTPD was conducted over a three-month period from mid-March to mid-June 2016. Researchers took temperatures reading inside and outside the LTPD and collected feedback from end-users and decision-makers. Real vaccines were stored in the device during this test; however, these vaccines were not used for immunization services.

The Sure Chill LTPD is one of the long-term passive cold chain technologies in the new WHO PQS category of long-term vaccine cold boxes and the first to acquire Grade A user-independent freeze protection. This device has the potential to increase immunization services provided by staff in health facilities where there is no access to proper electricity, or to potentially reduce the operating costs of the vaccine supply chain by upgrading from the solar or absorption equipment with lower-cost, long-term passive vaccine coolers.

All head nurses involved in this evaluation reported that the LTPD was an easy-to-use technology that maintained vaccine storage temperatures of 2°C to 8°C and which they thought not only had a potential role in their facility but which they thought could play a significant role in other health facilities.

One interesting facet of this study was the variation in the duration of the meeting time for the remaining ice at the end of the study. A difference of 11 days between the earliest and the latest LTPDs to exceed 8°C (46.4°F) after the study ended on July 13, 2016.

Researchers searched for but could not see a relationship between the duration variation and the variation in ambient temperature, nor in the geographical distance from the district health center. The time required for ice delivery wasn’t recorded in the study and so could not be verified. It might be that some study sites removed coolant packs for other uses after it officially ended, which could have accounted for a shorter total length of cooling time.

The importance of limiting equipment openings to five minutes was emphasized by three of the six equipment users as an important training message. Therefore, the future training materials used for equipment evaluations must be revised to ensure that equipment users distinguish the five-minute opening protocol as a simulation exercise instead of being a lesson about vaccine handling. While any person of any cold chain equipment should restrict the number and duration of equipment openings, the equipment evaluation protocol did not specify a vaccine handling policy on equipment openings.

Maintaining Temperatures On And Off The Grid

Keeping heat-sensitive vaccines and other drugs at the right temperature is crucial yet often difficult in areas with limited or no electrical power.

Many countries, including the United States, still have domestic-style refrigerators that are untested and have never been monitored for storing vaccines. As a result, incurring significant losses due to poor temperature control. The WHO Performance, Quality and Safety (PQS) program established equipment standards and testing protocols for vaccine storage, including electric, ice-lined, gas/kerosene, and solar-powered models.

 The WHO suggests the purchase of PQS-prequalified refrigerators. But many countries ignore the suggestion and opt to purchase locally available refrigerators because they are less expensive, are more readily available employ front-opening doors, and can be repaired by the local service technicians.

Unfortunately, few of these domestic-type refrigerators are able to meet the standards in safe vaccine temperatures. Past experiences have shown that domestic refrigerators have widely varying degrees of temperature and can harm the vaccines to freezing temperatures and rapid warm-up after power failures. The incessant use of domestic refrigerators needs to have better temperature monitoring to isolate problem areas in refrigerators before they compromise the vaccines.

An example of which is in Tunisia Optimize is working with Centre Technique des Industries Mécaniques et Electriques, a government-sponsored laboratory, to evaluate and create WHO PQS protocols to determine typical domestic refrigerators that have been used for vaccine storage or are considered for future operations. Domestic refrigerators presently in use are also being monitored. The results will help Tunisian policy-makers assess the option of using domestic refrigerators, and laboratory testing of new models will identify any risks as well as to inform suggestions for maintaining acceptable temperature control.

If no suitable refrigerator or solutions can be identified, decision-makers have the basis to develop improved models in the country or to purchase WHO PQS-prequalified refrigerators. The demonstration in Tunisia is to convey to all countries using domestic refrigerators that first, they should all be continuously monitored when operating; and second, the domestic refrigerators should be up to standard, and their performance confirmed before purchasing.


As the need for longer-life, larger-capacity cooling technologies are more in demand today, more manufacturers are starting to shift in that direction. Right now, there are at least two new passive devices under development by different manufacturers. These devices may allow for a cold life of more than 30 days. Each country has a unique set of challenges to overcome and user feedback that can be considered in product design and training.

If the new cooler works, it could revolutionize the way vaccines are administered in the developing world. Reliable, low-power refrigeration means that it would be possible to administer more effectively immunizing people against preventable diseases, even in places that don’t have steady power.

The Sure Chill LTPD did well in Khombole district, Senegal, between March and June 2016. Temperatures were kept within the desired range for vaccine storage, and regular ice replacement was enough for ongoing performance. For future study, the topic must include more actual door-opening patterns during the use of the devices in real-life situations and/or the effect of removal of ice packs for use in remote immunization trips. It would also be worth noting the monitoring of the condition of the ice packs changes when they travel from the district to the health posts.

There is an urgent need for simple, reliable cold storage devices that do not require power and allow medical staff to augment and extend vaccination services to children in the most isolated places in the world.

Reference Links:







Leave a Reply

Your email address will not be published. Required fields are marked *