February 2006, VOLUME117 /ISSUE 2


Huang et al. Post-PCV7 Changes in Colonizing Pneumococcal Serotypes in 16 Massachusetts Communities, 2001 and 2004. PEDIATRICS 2005;116:e408–e413.

An error appeared in the article by Huang et al, titled “Post-PCV7 Changes in Colonizing Pneumococcal Serotypes in 16 Massachusetts Communities, 2001 and 2004,” that was published in the September 2005 issue of Pediatrics Electronic Pages (2005;116:e408–e413). The authors reported serotype and resistance data on pneumococcal isolates from young children in 16 Massachusetts communities sampled in 2001 and 2004. In doing additional genetic analysis of these isolates, they discovered a small number (4.6%) with a discrepancy between the serotyping result based on antibody reaction (historically, the gold-standard method) and the serotypes suggested by the genetic sequence types.1

The authors repeated antibody-based serotyping of discrepant strains and have found most mismatched serotypes to be those predicted by genetic analysis. The serotype reassignments have resulted in small (mostly single- integer) changes in the percentages of specific serotype groups reported in the article. The key findings of the paper remain unchanged, both in terms of clinical and statistical significance. Nasopharyngeal carriage of non-PCV7 strains has increased, antibiotic resistance within non-PCV7 strains has increased substantially, and the resistance rates among isolates included in the PCV7 vaccine, those potentially cross-reactive, and those not included in the vaccine remain as previously reported.

Nevertheless, it is worth noting changes in some of the reported numbers of individual serotypes and their resistance profiles. The authors provide a corrected Fig 2 to reflect changes in 17 of 369 reported isolates, resulting in small changes in any given serotype. Although statistical significance remains unchanged for most serotypes, the authors do report 2 serotype groups (6A, Other) that now show a statistically significant difference, and 4 serotype groups (9A, 19A, 23A, 29) that change from a statistically significant difference to a trend toward significance.


Distribution of pneumococcal serotypes as a percent of total serotypes in 2001 shown in comparison to that in 2004. P values for Fisher's exact tests demonstrating trends and significant changes between serotype-specific proportional carriage in 2001 and 2004 are shown. Hatched bars represent the proportion of isolates for a given serotype that are nonsusceptible to penicillin.