Role of the natural immunity to diphtheria in preventing an outbreak of the disease in the community.

PIP: The presence of immunity to diphtheria in children with no history of diphtheria vaccination from Tambon Chiang Rak Noi, Bang-Pa-In District, central Thailand was determined by Schick tests and throat and skin cultures. 69 or 36.3% of 190 children aged 1-9 had negative, or immune, Schick tests. 39 children showed Corynebacterium organisms, 6 of which were positive for C. diphtheriae. 37 of the positive isolates were from throat swabs, 3 of them were from skin lesions, and 1 child had positive cultures of both throat and skin. Diphtheria organisms are known to persist in the mucous membrane of the nose and throat for years in about 1% of convalescents of the disease.^ieng