Unexpected responses of actively immunized men to a boosting dose of tetanus toxoid.

LITTLE work has been done to determine the effect of successive injections of tetanus toxoid in individual persons. Ina study' of a small group of ,adults actively immunized with tetanus toxoid, Evans (1943) found that in no instance was the antitoxin titre eighteen months after the third injection lower than it was four months after the second; in four of eleven persons it was definitely higher. The second injection was given nine weeks after the first, and the third injection ten months after the secqnd. During a recent investigation into methods for the prevention of clinical , tetanus, we have been able to study the effect of boosting d~ses on men who had received varying numbers of injections of tetanus .toxoid previously. Some results have already been, reported and are in ,course of publication in the Proceedings of the Royal Society of Medicine (Sachs, 1952). The work, recorded here was not reported owing to shortage of time, and appears to l!-S to be of sufficient interest and importance to justify the publication of a short note.,The results of the complete investigation will be published in the near future. , This part of the investigation was 'designed to determine the effect of a boosting dose of toxoid injected either alone or at the same time as 500 units of tetanus antitoxin given ina 'different site. The volunteers concerned were bled before and at certain fixed times after injection, a few being bled as late as six months after injection so that an idea of the duration of immunity could be obtained from measurement of the antitoxin 'titre at 'this time. It should be . I· /