Immunization schedule for Hib vaccine as recommended by IAP varies with age. This schedule of lessening number of doses of vaccine with increase in age is based on the premise that natural infection induces some immunity and so less number of vaccine doses are needed with increase in age.

Why do we not recommend one dose of rotavirus vaccine only (instead of 2 at present) if a child comes for vaccination at 4 to 6 months of age on the premise that the child may have developed partial immunity by rotavirus infection by this time?