Keep cool and carry on: the challenge of protecting vaccines despite power outages

A fridge designed for vaccines and medicines has “harnessed the power of nature” to keep its contents cold, even with intermittent access to electricity.

Vaccines are often temperature sensitive, with inoculations for diseases including hepatitis, typhoid and polio sensitive to both high and low temperatures.

This presents a major challenge for health workers dispensing vaccines across the world, particularly in areas with limited or unreliable electricity supplies.

But Sure Chill, a British technology and energy company based in Cardiff, has developed a fridge which “harnesses the power of nature” to protect sensitive medical supplies from power cuts.

The fridge, which has almost 20 models and is used in 49 countries, is based on the principle that water is heaviest at 4°C. A cold compartment in the fridge is surrounded by water, which cools when connected to power and forms a layer of ice above the chamber.

When electricity is switched off, the warm water rises while the ice begins to melt, keeping the water at a constant temperature. It can keep the contents chilled for up to four weeks without power.

“We’ve harnessed nature within a fridge,” Nigel Saunders, chief executive of Sure Chill, told The Telegraph. “In a frozen lake, water would be 4°C – the ice would be sub-zero, but the water will still be 4°C [as] water is densest at this point. So when the power drops out, the ice keeps the water at a steady 4°C temperature.”

The fridge, which is manufactured by companies in India and South Africa and has kept more than 20 million vaccinations cold, has been approved for use by the World Health Organization. Models, including cold boxes, cost between $700 and $5,000 and can be used along with solar panels or traditional mains electricity.

Both Unicef and Gavi, the Vaccine Alliance, currently buy the fridges and the company was given a boost when Mr Saunders joined Theresa May on her trip to sub-Saharan Africa last summer – a visit that proved infamous thanks to the then Prime Minister’s dance moves.

“We are used in a whole range of locations around the world – in hospitals, in clinics, in off the grid locations where they might have a power cut once a day,” said Mr Saunders.

“In Tanzania… I met one nurse in this little village who had to jump on her bike, cycle to the clinic and put vaccines in a cool box to cope with the power loss when the electricity went down. Installing our equipment has changed her life.”

But the fridge’s capacity to maintain a constant temperature is just as important as the ability to withstand power outages.

In June, the WHO announced that it was suspending the use of eight vaccine fridges manufactured by the Danish company Vestfrost, because it received reports that the fridges had “a tendency to freezing” and had “failed to meet the criteria for temperature control”.

Most vaccines must be kept at a temperature between 2°C and 8°C.

“One of the biggest problems [in cold chains] is actually the freezing of vaccines,” said Mr Saunders. “If you freeze a vaccine you destroy potency, and the problem is that no one really knows how many times a vaccine has been frozen before it is administered.

“So if you are installing equipment that freezes vaccines, you’ve got no idea if people are being immunised or not.”

But other technology is also being developed to protect temperature-sensitive vaccines, said Dr Marco Gaudesi, pharmacist and cold chain expert at Médecins Sans Frontières, an NGO supplying medical care and equipment in some 70 countries worldwide.

“Most vaccines are temperature sensitive. This is already challenging in the European supply chain, but then it becomes even more challenging elsewhere – especially when we run outreach vaccine campaigns, that last mile is particularly hard.

“We are always looking for new technology to use,” Dr Gaudesi added, though he did not comment on the Sure Chill fridge.

“We recently developed a tool to monitor the temperature in fridges and send us text alerts – this is for us a big advantage because we can constantly monitor the standard and quality of the vaccines that we store,” he said. “Solar powered devices are also pretty crucial.”

Protect yourself and your family by learning more about Global Health Security