Challenging requirements in resource challenged environment on a time challenged schedule: A technical solution to support the cold chain for the VSV-Zebov (Merck) Ebola vaccine in Sierra Leone Guinea

Abstract

In an effort to combat the spread of Ebola in West Africa, phase II/III clinical trials of the vaccines developed by Merck/Newlink Genetics and GSK were expedited. As a result, normal vaccine efficacy as a function of temperature tests have yet to be conducted, leaving temperature requirements of -60C to -80C, significantly colder than EPI vaccine temperature requirements of 2-8C. The trials were held in severely resource challenged regions, with erratic and limited electrical power and no access to dry ice. Intellectual Ventures Laboratory/Global Good modified the Arktek passive vaccine storage device from its original design point of 2-8C down to the required -60 to -80C. A comprehensive series of risk reduction experiments and analysis were performed to verify that the Arktek device could withstand increased stress due to differential thermal expansion and to identify any materials at risk due to reaching glass transition temperatures. The DF (Deep Freeze, modified for use at -80C) Arktek, when combined with an alcohol based phase change material (heat of fusion 110 kJ/kg, freezing temperature -78C) maintained temperatures <;-60C for 6.5 days in 43C ambient with a heat leak of 2.2 W. Combined with -80C freezers in capital cities, a robust vaccine cold chain was deployed in Sierra Leone and Guinea.