Distribution of pneumococcal types in the Stockholm region 1976--1978.

During 1976--1978 1347 pneumococcal strains from 3 bacteriological laboratories in the Stockholm region were typed using antisera from the State Serum Institute; Copenhagen, Denmark. Typing was done with immunoelectroosmophoresis (IEOP), which has been found to be a simple and reliable method for this purpose. In the whole material types 6, 23, 19 and 3 were the most common, accounting for 21, 18, 17 and 12%, respectively. Types 6, 19 and 23 dominated greatly in children less than 7 years, accounting for 67% of the isolates; a more even distribution with type 3 as the most frequent (16%) pneumococcal type was seen in people greater than or equal to 15 years. In relation to their overall frequency, type 4, and to a lesser degree types 3, 8 and 9, were more often isolated from blood and spinal fluid. Types 3 and 9 were also more frequently isolated from patients with pneumonia than from pneumococcal carriers, while types 6 and 19 were more frequent in carriers. Types represented in the recently introduced 14-valent pneumococcal vaccine constituted 70--86%.