At what age is Hepatitis A vaccine first licensed?

The Hepatitis A vaccine is first licensed for administration to children starting at 12 months of age. This timing allows the vaccine to be effective in inducing an adequate immune response while ensuring that the child's immune system is sufficiently developed to respond to the vaccine appropriately. Prior to this age, infants and younger children may not develop the desired immunity effectively due to their still-maturing immune systems. The recommendation for vaccination starting at 12 months also aligns with public health policies aimed at preventing the transmission of the hepatitis A virus, particularly in at-risk populations and during outbreaks.

The other age options suggest administering the vaccine either too early, when the immune response is not optimal, or too late, which could miss critical vaccination periods for prevention during childhood.