Serogroups and serotypes of pneumococci in Montreal: correlations with age, outcome and indications for vaccination.

The serogroups or serotypes of 262 pneumococcal isolates obtained from the blood and other body fluids of 260 patients in the Montreal area during a 3-year period were determined. The distribution of the 30 different serogroups detected was generally similar to what has been reported in other Canadian provinces and in the United States. However, the distributions in pediatric patients (less than 18 years old) and adults were significantly different (p less than 0.001). Serogroup 15 was relatively frequent in the adults. In the pediatric patients 88% and 91% of the 150 isolates were related to the 14-valent and the new 23-valent vaccines respectively. In the adults the comparable proportions were 70% and 89% of the 112 isolates. The mortality rate was 6% in the pediatric patients and 41% in the adults. Previous use of pneumococcal vaccine in the pediatric patients would have prevented only one death because most were less than 2 years old or did not have conditions regarded as indications for vaccination. Such underlying diseases were found in 58% of the adults, though. The mortality rate was 26% in the adults who were less than 65 years of age and were without these underlying conditions but rose to 65% in older patients; the difference was statistically significant (p less than 0.02).