Single massive dose of vitamin A for preventing the deficiency in preschool children between the age of 1-6 years for every 6 months is:

Prevention and control of vitamin A deficiency in children  It  is  estimated that large  number of children suffer from sub-clinical deficiency of vitamin A.  Under the programme, doses of vitamin A are given to all children under 5 years of age. The first dose (1  lakh units)  is given at nine months of age  along  with  measles  vaccination.  The  second  dose (2  lakh  units)  is  given  after  9  months.  Subsequent  doses (2  lakh  units  each)  are  given  at six  months  intervals  upto 5  years  of age.  All  cases  of severe  malnutrition  to  be given one additional dose of vitamin A.