The serological assessment of a tetanus toxoid field trial.

To determine the effectiveness of a method for controlling tetanus neonatorum, a double-blind controlled trial involving 1 618 women was conducted between 1961 and 1966. Women in the study were given 1-3 injections (1 ml) of aluminium-phosphate-adsorbed tetanus toxoid or a placebo (influenza vaccine). At the conclusion of the trial, 5-ml samples of blood were obtained from 299 women. Sera were titrated for anti-tetanus antibodies by two methods.A comparison of the clinical and laboratory results showed a close relationship. It is suggested that the level of protection may be lower than is at present accepted. Antitoxin levels were inversely related to age and directly to the interval between injections. Two widely spaced injections (8 months or more) may be about as effective as 3 injections. One injection of specially prepared toxoid with a high immunizing potency might give significant protection.