Rational approaches to reduce adverse reactions in man to vaccines containing tetanus and diphtheria toxoids

Adverse reactions to routine vaccines are obstacles to the mass vaccination campaigns. Though the absolute safety of any injectable vaccine cannot be guaranteed, the adverse side effects to vaccines can be minimized by practicing existing scientific knowledge. Adverse side effects to tetanus and diphtheria toxoids have been known for many years and there have been ways to minimize these reactions. These procedures did not get wide acceptance, because the current partially purified tetanus and diphtheria vaccines meet the regulatory requirements and the manufacturers are reluctant to change the established procedures of production due to the amount of work involved in the regulatory issues under the current Good Manufacturing Practices (GMP). Due to the recent epidemic of diphtheria in the independent states of the former Soviet Union, and its potential for spread to other European Countries, vaccination campaigns with tetanus and diphtheria vaccines received a new boost with several international agencies. In this report, we review the causes for adverse reactions to tetanus and diphtheria vaccines and offer practical suggestions for minimizing these reactions. The major issues in minimizing adverse reactions to these vaccines include: (1) purifying the toxins before detoxification as the reactogenic accessory antigens get covalently bound to the toxins during detoxification; (2) either using well-tolerated adjuvants which do not elicit the production of antigenic specific IgE antibodies responsible for adverse reactions or by using non-adjuvanted highly immunogenic polymerized antigens; (3) checking the status of immunity by recently developed rapid serological methods or by the Schick skin-test for diphtheria to avoid allergic or Arthus-type reactions. These approaches are applicable to industrial scales and would result in a pure, less reactogenic and better characterized toxoids antigens which would be more suitable for combined vaccines comprising highly purified acellular pertussis components, polysaccharide-protein conjugates and other antigens.