Vaccine not given between 0-6 months is-

.the principal problem of measles immunization is timing,immunization before the age of 9 months runs the risk of the vaccine being rendered ineffective by the natural antibodies acquired through the mother.immunization later than 9 months means that a significant propoion of children will contract measles in the interval between wearing off natural protection,and the introduction of the vaccine. ref:park&;s textbook,22 nd ed,pg 140