Abstract: The drinking water-based avian coccidiosis vaccine formulation and delivery system is structured to deliver a vaccine containing live Eimeria oocysts to poultry house brood chamber chicks. The vaccine is delivered to the chicks in a diluted form through the poultry house drinking water system. The chicks are inoculated with the drinking water-based avian coccidiosis vaccine when they consume the water containing the vaccine. The timing of the chicks' drinking water access to the diluted drinking water vaccine is critical. During the inoculation process, water is temporarily withheld from the chicks for a waiting period of about 3-5 hours, and access to the diluted drinking water-based vaccine is limited to an accessibility period of about 2 hours. Additionally, metering valves and/or terminal metering valve assemblies are manually or automatically closed when the when the drinking water lines are fully charged with the diluted vaccine.