Abstract: Vaccine formulations comprising polyglycerol polyricinoleate (PGPR) are disclosed. Certain disclosed exemplary vaccine formulations comprised an aqueous phase comprising inactivated bacteria and/or viruses, and/or bacterial and/or viral antigens. One particular embodiment comprised an inactivated H9N2 PGPR emulsion-based vaccine for day-old chicks. Disclosed PGPR-based vaccine formulations can be administered alone, or in combination with or as a composition including a second standard fast release vaccine. Disclosed vaccines delay antigen release, and therefore delay an immune response in a subject receiving the vaccine, typically by 7-35 days. The present invention also concerns a method for vaccinating a subject, such as poultry or fish, with disclosed vaccine formulations, as well as a method for making PGPR-based vaccine formulations.