Cold Chain management starts from vaccine manufacturing down to vaccine administration. Every step is crucial and full of risks including the intermediary steps during transport and delivery. It’s especially the case in temperature control and monitoring wherein the vaccines should be stored and transported within a safe temperature range (2℃ to 8℃).
This safe temperature range is important in ensuring the effectiveness and potency of vaccines. For example, vaccines for Hepatitis A, Hepatitis B, human papillomavirus and Meningitis C have high freeze sensitivity. In other words, these vaccines should never be exposed to zero or subzero temperatures and ice should not be used for transport. On the other end of the scale, some vaccines have high heat sensitivity – for polio, influenza, cholera and measles (source: World Health Organisation). Outside the safe temperature range and with improper storage and transport, vaccines can become ineffective and even unsafe which can affect the saving of thousands or millions of lives. Even with preventative measures in place for a potential cold chain breach, it’s always ideal to focus on prevention of such breach (and maintain safe temperature range) to avoid potential financial losses and help ensure the health of many.
Challenges in cold chain management
One of the main challenges is about tight temperature control. Extreme temperatures (especially in prolonged periods) can ruin an entire batch and make them unfit for use. The integrity of the vaccines gets compromised, which then delays the delivery of lifesaving products to key areas. The production and delivery of the next batch of needed vaccines might take longer than expected.
As a result, it’s important to ensure tight temperature control. Storage guidelines are continuously being updated and better temperature indicators are being designed to help maintain safe temperature ranges as well as indicate whether the vaccines are compromised during transport and storage. For example, there are appropriate indicators that show if a product has been exposed outside the ideal temperature range. With a prominent visual notification, the recipients can immediately tell if the products were compromised. For vaccine storage management, the recent creation and implementation of ‘Strive for 5’ in the National Vaccine Storage Guidelines help maintain the integrity of vaccines during storage and transport. Striving for 5℃ (midway the 2℃ to 8℃ safe temperature range) is a reasonable number to aim for since as mentioned earlier, there are certain vaccines with high heat or freeze sensitivity. Subzero temperatures can destroy most vaccines, and temperatures even a bit beyond 8℃ can decrease the viability and efficacy of vaccines. The guidelines also discuss the benefits and uses of purpose-built vaccine refrigerators (e.g. stable and uniform cabinet temperature, with alarm and safety features to alert us of temperature fluctuations). For additional measures, the guidelines also discuss the use of data loggers, thermometers, alarm systems, automated temperature-monitoring systems (with wireless monitoring for almost real-time monitoring) and disposable cold chain monitors. The use of one or a combination of these devices is important for quality control and assurance, especially if one system fails.
Hidden challenges and potential errors
Proper cold chain management is straightforward as long as there are tight temperature control and strict compliance with other safety protocols. However, small neglected details can also compromise vaccines.
For example, a vaccine refrigerator may have been accidentally disconnected from the power source. This would cause the temperature to rise and thereby destroy some of the vaccines. Also, even when the vaccine refrigerator is reconnected immediately, it still takes time to lower the temperature again and stabilise the temperate levels. There are also cases when no one has noticed that the power source failed during transport or storage, or the vaccine refrigerator has been disconnected from the power source for too long (and then someone else reconnected it). As a result, no one knows or has been notified that the vaccines have potentially been outside the safe temperature range for an extended period of time. The vaccines are still administered, but the viability and efficacy are questionable.
Reliable indicators and monitoring systems are crucial in such cases. This way the recipients and healthcare organisations can ensure the integrity of the vaccines and that these are transported and stored within the safe temperature range. The use of indicators and monitoring systems is an additional measure since the priority is still on ensuring the refrigerator is connected to a reliable power source and that the internal temperature is stable and uniform. Back-up plans are often required in anticipation of a power failure, a back-up power supply (e.g. battery back-up, generator) or back-up coolers are in place for emergencies. The back-up plans are also documented so that the person can immediately act during power failures.
In the case of receiving a vaccine delivery, there are also measures and protocols in place to ensure the integrity of the shipment. For instance, receiving a delivery involves checking the heat and cold monitors, verifying the refrigerator temperature is within 2℃ to 8℃, immediately placing the vaccines inside the fridge for refrigerated transport, rotating the stock and making sure that the delivery received matches the placed order.
It’s a rigorous process since lives are at stake and a single missed immunisation can potentially derail a child’s future. In addition, failure to maintain temperature levels also indicates a lot about the integrity of the entire cold chain. It also makes us question the integrity of previous and future deliveries. Although there might be effective measures in place for dealing with a cold chain breach, the integrity of the entire storage and transport process should be solid, or if there’s a breach or mistake, it is properly indicated and documented to prevent the use of the compromised vaccine.
