The recomended guidelines are that you should have the full course of 5 omjections against Tetanus to develop full immunity. Normally these are given at 2, 3 and 4 months, then just prior to starting infant school and just prior to completing secondary school. Further injections are only given if someone has not had the full 5 injections or if an injury is particuarly deep and dirty. A Tetanus injection should be given within 2 days of injury.