Zoetis – Fostera™ PRRS Fostera™ PRRS is for vaccination of healthy, susceptible swine 3 weeks of age or older in PRRS virus-positive herds or seronegative pigs deemed at risk for exposure to PRRS virus as an aid in preventing disease associated with Porcine Reproductive & Respiratory Syndrome Virus, Respiratory Form. A 24-week duration of immunity has been demonstrated. More than half of weaning-age PRRSV-negative pigs become infected with PRRSV before going to market 2. Implementing measures, including vaccination with Fostera™ PRRS, helps growing pigs defend themselves against a PRRSV challenge. 1. 2.Holtkamp D, Kliebenstein J, Zimmerman J, Neumann E, Rotto H, Yoder T, Wang C, Yeske P, Mowrer C, Haley C. Assessment of the economic impact of porcine reproductive and respiratory syndrome virus on U.S. pork producer.