Geoffrey Edsall

Combined Tetanus-Diphtheria Immunization of Adults: Use of Small Doses of Diphtheria Toxoid

prone occasionally to show untoward reactions to diphtheria toxoid (e.g.1). Incidence of such reactions can be reduced by either (1) immunizing only the susceptibles as determined by Schick testing, (2) use of purified toxoid, or (3) reducing the dose of toxoid administered. The first method is tedious and time-consuming and involves a tremendous amount of organization and labor when large groups are involved. In fact, it is widely felt that Schick testing is even more inconvenient than toxoid injections in adults, although it does reduce reactions. The second method is of great value, but it is by no means sufficient to eliminate all severe reactions.2 The third method has attracted several investigators, but it is open to the logical question: Will small doses of toxoid provide a sufficient antigenic stimulus to protect the recipient? Danish and Canadian investigators were the first to explore this approach systematically. Scheibel and Tulinius 3 showed that as little as 1 Lf of diphtheria toxoid, adsorbed onto aluminum