- If an immunisation is given too early (e.g. if measles immunisation is given at 3 months), the infant may not develop the expected resistance to the illness due to the immune system still being too immature to respond fully.
- If an immunisation is given too late (e.g. not giving measles immunisation at 9 months), the infant may develop that illness before the immunisation can be given.
- If immunisations are given too soon after the previous immunisation (e.g. if DPT immunisations are given a week apart), the infant may not develop the expected resistance to the illness.
All the most important immunisations should be given by the time the child reaches 9 months of age.
It is important to give immunisations at the recommended time according to the immunisation schedule.