Design and Testing of a Thermoelectrically-Cooled Portable Vaccine Cooler

and expiration --can be as high as 60-70% (Wallace, Willis, Nwaze, & Dieng, 2017; Zaffran et al., 2013). Although vaccine coolers are designed to keep vaccines cold, a poorly designed apparatus can result in accidental freezing of vaccines so that sub-potent vaccines can sometimes be administered (Chen, & Kristensen, 2009). A 2007 study found that in vaccine reports tracked longitudinally, 75-100% of vaccines were exposed to freezing temperatures; the authors recommend im-proved cold-chain transport equipment as a solution (Matthias, Robertson, Garrison, Newland, & Nelson, 2007). Vaccine freezing or overheating issues are not relegated solely to older studies or developing nations. The 2013-2014 H1N1pdm09 virus outbreak in the United States can likely be attributed to vaccine shipments being exposed to high temperatures (Caspard, Coelingh, Mallory, & Ambrose, 2016). The cost of most vaccines today ranges from $3.50-$7.50 per administration (Gates, 2012), so wastage results in a considerable economic loss. Importantly, when vaccines lose potency, there is a loss of confidence in vaccine therapy (Larson, Cooper, Eskola, Katz, & Ratzan, 2011). Thus, reducing vaccine wastage while in-creasing potency will provide more effective immunization in the rural, developing world at a reduced cost per dose. One way to address aspects of the wastage issue is the development of small coolers capable of transporting vaccines, maintained in the proper temperature range, from the regional health center to the distant client; this trip is termed the end stage of the cold chain. Coolers employing phase change materials including ice are capable of maintaining the desired temperature range for a period, but vaccines in such coolers are sometimes subject to overheating or freezing because of the lack of temperature regulation. INTRODUCTION Vaccines are a major economic cost and component of the worldwide battle against infectious disease. In 2011, UNICEF bought 2.5 billion doses of vaccines, and spent more than one billion dollars on vaccines (UNICEF, 2011). Within the category of develop-ment assistance for maternal and child health, donors spent $3.2 billion on child vaccines in 2014 (Dieleman, Murray, & Haaken-stad, 2015). Still, for children in developing countries, health care inequities are prominent, and access to preventative therapies and drugs is limited (Gates, 2012). One reason these countries lack enough vaccination coverage is due to insufficient cold storage (without freezing) in the vaccine supply chain (Humphreys, 2011). Breakdown of the vaccine cold chain is believed to be a major contributor to late 20th-century polio outbreaks in southern Africa (Schoub, & Cameron, 1996). Many vaccines must be maintained in a temperature range of 2-8°C to remain potent. Indeed, previous studies have shown that cold chain wastage--due to the failure to maintain vaccines in a safe temperature range, the need to discard unused portions of opened vaccine vials, and improper handling Design and Testing of a ThermoelectricallyCooled Portable Vaccine Cooler