Porcine reproductive and respiratory syndrome virus (PRRSV) is the major cause of reproductive and respiratory problems in pigs worldwide. Controlling this disease is a top priority in pig producing countries. Due to mutations at a high frequency, new variants of the virus appear that are no longer effectively controlled by the commercial vaccines. In addition, highly virulent variants emerge, leading to high losses. With regard to animal welfare and agricultural economics, there is an urgent need to control PRRS. Furthermore, the abusive use of antibiotics to control PRRSV-associated respiratory problems may lead to resistance that may endanger public health. PoRRSCon is an initiative of 14 partners originating from Europe and Asia with strong expertises in virology and immunology. They are doing frontline research on PRRSV and/or vaccine development. Two of these partners are leading European pharmaceutical companies that will guide the consortium in the direction of exploitable results. By joining their strengths they have an ideal position to be successful in one of the most difficult challenges in pig health, controlling PRRS. To reach this final goal, the following objectives are forwarded:(i) characterize genetically and antigenically current PRRSV isolates in Europe and Asia, (ii) have a better understanding of the complex pathogenesis of PRRSV infections, immune response against PRRSV and immune modulation by PRRSV, (iii) define the genetic base of PRRSV virulence, (iv) identify PRRSV proteins and domains on these viral proteins that are involved in the induction of the immunity against PRRSV and in the immune modulation of PRRSV, (v) develop new generation, efficacious and safe marker vaccines that can be adapted to temporary changes and geographical differences and (vi) develop DIVA assays that allow to differentiate infected from vaccinated animals. At the end, it will be possible to set up a control strategy by combining marker vaccines with DIVA assays