Reducing the loss of vaccines from accidental freezing in the cold chain: The experience of continuous temperature monitoring in Tunisia

Abstract

Accidental freezing of vaccines is a growing threat and a real risk for national immunization programs when the potency of many vaccines can be compromised if these are exposed to sub-zero temperatures in the cold chain. In Tunisia, this issue is compounded by using sub-standard domestic cold chain equipment instead of equipping the program with medical refrigerators designed specifically for storing vaccines and temperature sensitive pharmaceuticals. Against this backdrop, this paper presents the findings of a demonstration project conducted in Tunisia in 2012 that tested the impact of introducing several freeze prevention solutions to mitigate the risk of accidental freezing of vaccines. The main finding is that, despite the continued use of underperforming domestic refrigerators, continuous temperature monitoring using new technologies combined with other technological interventions significantly reduced the prevalence of accidental exposure to freezing temperatures. These improvements were noticed for cold chain storage at regional, district and health center levels, and during the transport legs that were part of the demonstration conducted in the regions of Kasserine in the South-Eastern part of Tunisia. Subsequent to introducing these freeze prevention solutions, the incidence of freeze alarms was reduced and the percent of time the temperatures dropped below the 2 °C recommended threshold. The incidence of freeze alarms at health center level was reduced by 40%. Lastly, the solutions implemented reduced risk of freezing during transport from 13.8% to 1.7%. Although the solution implemented is not optimal in the longer term because domestic refrigerators are used extensively in district stores and health centers, the risk of accidental freezing is significantly reduced by introducing the practice of continuous temperature monitoring as a standard. The management of the cold chain equipment was strengthened as a result which helps protect the potency of vaccines to the areas of most difficult access.

On-farm storage of livestock vaccines may be a risk to vaccine efficacy: a study of the performance of on-farm refrigerators to maintain the correct storage temperature

“…Therefore, placing the farm’s fridge in a controlled temperature room could improve a fridge’s capability of stabilizing its internal temperature. The results from this research go in line with other recent studies where weaknesses of domestic fridges used to store human vaccines, a common finding in developing countries, were also been found [ 9 , 25 ]. More comprehensive studies, with a larger number of fridges are needed in order to fully understand the scale of the problem.…”

“…Vaccines stored at different temperatures could result in potency loss and impaired efficacy [ 5 – 7 ]. Furthermore, emphasis is being increased nowadays on vaccine management to protect vaccines from freezing [ 8 , 9 ] as cold chain practices tend to prioritize protecting vaccine from heat damage. Very often the risk of vaccine exposure to temperatures below freezing point is considered greater than heat exposure [ 10 – 12 ].…”

Collective construction of bundle for immunobiological agents conservation best practices

“…There is evidence that the use of electronic recorders brings highly significant improvement, especially at the local level, as it allows health professionals to identify changes during the day/ night cycle, including weekends and holidays. Thus, the health professional can determine if there have been unacceptable temperature exposures and thus make informed decisions as corrective measures to reduce and/or eliminate cold chain problems (6,20,22) .…”

“…Most middle-income countries have cheaper, home-type refrigerators that are designed to reduce heat exposure primarily; these countries were more effective in this, but less effective in reducing freezing damage. They present significant performance weaknesses that clearly impact the quality of the handling of immunobiological agents, the equipment's lifespan and reliability of the cold chain (22,28,30) .…”

Cold chains, interrupted

“…The only reliable way to verify the integrity of the cold chain is continuous temperature monitoring. While it is still common practice in developing countries that thermometers are put into refrigerators and temperatures are checked at given intervals (Thakker and Woods, 1992;Lloyd et al, 2015), only fridge tags, min/max thermometers and vaccine vial monitors can reliably provide information whether the safe range was maintained or breached (WHO, 2014;Trostle et al, 2003). The amount and complexity of vaccine campaigns, however, make vaccine tracking difficult: vaccines are often packed in small containers that cannot individually be monitored due to the high cost and effort in monitoring and updating temperature logs (Carullo et al, 2009).…”