In poultry medicine, vaccinating in ovo means injecting the vaccine into which site?

• A. Pullets
• B. Embryo in the egg
• C. Hen's uterus
• D. Newborn chick

Answer: (B)

In ovo vaccination is done by delivering the vaccine directly to the embryo inside the egg. This allows the developing chick to mount an immune response before hatching, typically by injecting into the amniotic cavity so the embryo encounters the antigen as it grows. So the vaccine is placed in the embryo in the egg, not into a pullet after hatch, the hen’s uterus, or a newborn chick.