The EC-funded RATIONALLY DESIGNED project aimed to develop the appropriate methodologies through which safe and efficacious vaccines could be successfully designed. The objective was to identify the immuno-protective antigens required for vaccine development as well as the appropriate delivery vehicles. One of the key aims of RATIONALLY DESIGNED was to examine the quality of immunity that is required to prevent disease. In other words, is any degree of immunity attributed to the vaccine considered to be effective? The qualitative aspects of this project are pioneering in the sense that new insight can be gained into rational vaccine design. Project partner CIDC-Lelystad evaluated the properties of adjuvants, used alongside vaccine to improve immune responses and overall enhance the efficacy of DNA vaccines. The use of plasmids encoding IFN-g or IL-12 as adjuvants were evaluated alongside CpG immunostimulatory motifs and DDA and SL-CD. DDA and SL-CD are commonly used adjuvants, employed to boost the effectiveness of vaccines. Research showed that DNA vaccines alongside DDA resulted in stronger immune responses compared to plasmid vaccination alone. Overall, the use of DDA as an adjuvant appeared to increase protection from clinical disease in the tested animals.