Antitetanus immunity in a sample of adult population from the Siena area (Italy).

1045 subjects (427 males and 618 females) from the Siena area, aged 20-85, were screened for tetanus antitoxin by the means of a passive haemogglutination assay. 32% of subjects was found protected against tetanus (antitoxin titre greater than or equal to 0.1 I.U./ml), 34.7% resulted partially protected (titre greater than or equal to 0.01 - less than 0.1 I.U./ml), and 33.3% was found unprotected (titre less than 0.01 I.U./ml). The protection rate was higher among males (44.9%) than among females (23%) and showed a definite age-related decrease. Within each age group, the protection rate was higher among males. The lowest protection rate (3.2%) was observed among females aged 70 or more. Analysis of the protection rate according to the individuals' occupation showed the highest value (44.9%) among workmen and the lowest (12.1%) among housewives. The anamnestic criterion was found exceedingly unreliable to assess the individual's immune status. Results, which are consistent with present tetanus italian epidemiology, are discussed for their implications relating to a possible improvement of current antitenus immunization policy.