Serotype 10A In Invasive Pneumococcal Disease Surveillance In New Jersey, April – September 2009

Background: Following the introduction of the seven-valent conjugate vaccine (PCV-7), invasive pneumococcal disease (IPD) caused by serotypes not included in PCV-7 has increased in a phenomenon known as serotype replacement. 

Objectives:   To describe results of a pilot project initiated by the New Jersey Department of Health and Senior Services (NJDHSS) to evaluate serotype replacement in NJ

Methods: IPD, defined as laboratory-confirmed S. pneumoniae infection from a normally sterile site, is reported through the Internet-based Communicable Disease Reporting and Surveillance System (CDRSS).  In April 2009, the NJDHSS requested that laboratories submit specimens on IPD cases for DNA amplification-based serotyping.  Specimens were matched to CDRSS IPD case records to obtain demographic and clinical information.

Results: During April 1–September 30, 2009, we received reports of 301 cases of IPD.  Clinical specimens were available for 150 (50%) of the cases; of these, 143 were serotyped.  Serotype 10A was identified in 12 of 21 counties in NJ and accounted for 25% of reported IPD, second in frequency only to serotype 19A.  Serotype 10A was the most frequent cause of IPD among adults 50 years of age and older (41% in adults 50-64 years old, 22% of cases in adults > 65 years). IPD due to serotype 10A was rarely seen in children less than 5 years old. 

Conclusions: Serotype 10A has not previously been reported to account for a substantial percentage of IPD in the United States.  The newly licensed 13-valent conjugate vaccine might have less effect on IPD burden in NJ than was seen after the introduction of PCV-7, given serotype 10A prevalence in initial surveillance.   A case-control study is currently ongoing to compare IPD cases due to serotype 10A with all other serotypes with respect to vaccination history, presence of an indication for pneumococcal vaccination, and disease severity.