Vacuum Insulation Maintains Drug Integrity
Vacuum insulation panel technology solved the military's problem of maintaining cold temperatures in its supply chain.
In late 1997, a batch of anthrax vaccine arrived at a U.S. Army facility in Germany spoiled by heat. This loss of a scarce resource prompted the Army to order personnel to treat all anthrax vaccine "like a nuclear device." In other words, very carefully.
Faced with the hazards of inadequate shipping, the Army put Wayne Williams, a former Army captain employed by Information Network Systems, a contractor for the United States Army Medical Material Agency (USAMMA), in charge of establishing a safe cold chain for heat-sensitive products.
Williams approached Anderson Clark, CEO at Thermal Systems International (TSI; Xenia, OH), the maker of a system that uses vacuum insulation panel (VIP) technology to slow heat transfer in both a portable vaccine refrigerator and a secondary passive delivery container. The passive container combines high insulation value with patented phase-change materials (PCMs) that thaw at nominal vaccine-maintenance temperatures.
In essence, VIPs are evacuated envelopes surrounding microporous cores. The cores have low thermal conductivity. When pressure within them is reduced enough, the pore divisions significantly interfere with heat transfer through any remaining air. This creates insulation values much greater than are obtained by conventional foams and at far less extreme vacuum than that found in dewars such as Thermos bottles. Insulation resistance (R) values of 20–40 per in. can be achieved in VIPs.
TSI's VaxiCool refrigerator system can operate with one 40-W solar panel and a 100-Ah lead acid battery.
In late March 1998, the Army subjected TSI's VIP-insulated system to independent testing by Key Scientific Inc. (Rockville, MD). Key Scientific reported the unit maintained temperatures for exceptionally long holdover times—long enough to keep a payload of anthrax vaccine within temperature limits to allow air shipping from the United States to Europe or South America without power. With battery power, the effective range extends worldwide.
Williams developed a cold chain model. Within the chain, vaccines are delivered by FedEx and DHL for consolidated storage in large refrigeration units known as Environtainers. Next, the VIP-insulated system provides end-use distribution of vaccine within and among large military installations. This role became critical when FDA stopped the manufacture of anthrax vaccine, making paramount the worldwide redistribution of existing surpluses.
In mid-1998, USAMMA designated the VIP-insulated system as an integral part of its supply cold chain. By November 1999, the General Accounting Office (GAO) reported that Williams's USAMMA cold chain was 99.8% effective. In addition, the GAO directed that all pharmaceutical vendors to the Department of Defense put in place similar delivery systems to U.S. military installations.
Because of their high R values, packages employing VIP technology and loaded with frozen gel packs, dry ice, or other PCMs stay cold up to eight times longer than same-size containers employing conventional insulation. According to Nick Wynne, chief engineer at VacuPanel Inc. (Xenia, OH), TSI's VIP supplier: "Some operations are impossible without VIPs. In practice, the use of VIP packaging to curtail heat damage to expensive heat-sensitive pharmaceuticals offers enormous dollar savings, especially for pharmaceuticals sent where handling is less than optimal. Most important is the potential to save lives by getting pharmaceuticals to regions where they were previously undeliverable."
VacuPanel is a member of the Vacuum Insulation Association (VIA; Arlington, VA). For more information about the VIA, visit www.vacuuminsulate.org.