AIPO4 adsorbed tetanus toxoid injected in rabbits according different vaccination schedules, gives rise to antibody responses with varying lag periods. Shortening the intervals among antigen injections, or increasing the quantity of toxoid per dose, makes it possible to reach protective serum antibody levels in 10 days. That is to say, in a period of time shorter than the mean tetanus incubation in man. Although difficult to transfer to man, the exposed data suggest a possible differentiated antitetanus vaccination in subjects at risk, non protected.