The primary serological response to a single dose of adsorbed tetanus toxoid, high concentration type.

Single-dose immunization against tetanus was studied in 511 previously non-immunized residents of rural villages in Upper Volta. Males and females were equally represented and a wide age range was covered. A single dose of adsorbed tetanus toxoid containing 17.5 Lf units of toxoid and 3.86 mg of aluminium phosphate per 0.5 ml dose was used. Blood samples were taken 7 days, 2 months, and 12 months after immunization, and serum antitoxin titres were determined by neutralization titrations in mice. Adverse reactions were negligible. Only 2 participants gave evidence of prior immunization by developing detectable antitoxin titres after 7 days; they were eliminated from the study. After 12 months, 59% of the participants had antitoxin titres of >/=0.01 IU/ml, a titre usually considered protective. The mean titre and the proportion of those protected decreased substantially with increasing age; overall, females gave somewhat greater serological responses than males. Mean titre increased by 25% between 2 months and 1 year after immunization; the increase was greater in females than in males. In children under 6 years of age, 100% of females and 82% of males had protective titres after 1 year.