Epidemiology and immunity to tetanus in Sweden.

An investigation of tetanus antitoxin titres in the Swedish population was carried out in 1985. In Sweden, primary vaccination against tetanus has consisted of 3 doses at intervals of 4-6 weeks, beginning in the 2nd or 3rd month of life. A booster dose is offered to school children at 8-10 years of age. Three levels of antitoxin concentration (0.01, 0.05 and 0.1 U/ml) are used to demonstrate different titre levels. The interpretation is based on the premise that a serum level of 0.01 U/ml is sufficient to protect the subject against clinical tetanus. A protective titre level (greater than 0.01 U/ml) was found in 98-99% of children and young adults. A rapid decrease in the number of children with high titres (0.05-0.1 U/ml) was observed after the age of 1 and was very low in the 4-5-year-old children. An increase in the number with titres of 0.05 and 0.1 U/ml was seen after the booster dose given at school. A protective level was detected in all 21-30-year-old men and in 94% of the women, in 94% of 31-50-year-old men and in 73% of the women in the same age group. 70% of 31-40-year-old men reached antitoxin concentrations of 0.1 U/ml, and 38% of the 41-50-year-olds. The corresponding figures for women were 22% and 16% respectively. In people over 60 years, 80% of the men and 56% of the women reached protective levels of antibodies.