Invasive Streptococcus pneumoniae (IPD) Serotype Project, Children Under Five, Oklahoma

Learning Objectives for this Presentation:
By the end of the presentation participants will be able to describe epidemiology of IPD in children under 5 in Oklahoma, understand the distribution due to vaccine preventable serotypes, and determine the number of preventable cases.

Background:
Since 2001, 3510 IPD cases were reported to the Oklahoma State Department of Health (OSDH), with children under 5 constituting 340 (9.7%) of those cases. The incidence of IPD nationally declined following introduction of a the pneumococcal conjugate vaccine (PCV7), which prevents infection by 7 pneumococcal serotypes. Because of low PCV7 uptake in Oklahoma, OSDH and the Centers for Disease Control and Prevention developed protocols to evaluate vaccination history and IPD serotypes.

Objectives:
The objective of this study is to determine occurrence of vaccine preventable IPD among children under 5 and the number of preventable IPD cases.

Methods:
Serotyping was performed by PCR on sterile site isolates beginning in November 2006. PCV7 vaccine histories were determined using the immunization registry, medical records, and physician and parent contact.

Results:
Sixty-nine cases of IPD were reported, with 54 isolates (78.2%) submitted for serotyping. Sixty-three percent (34/54) had at least one vaccination prior to disease, and 23 (68%) were age appropriately vaccinated. Forty-one (76%) isolates have been serotyped. Four isolates were PCV7 serotypes. Of these, one was age appropriately vaccinated at 3 months; two received no PCV7 and were potentially preventable; and the vaccination status of the fourth was undetermined. The most common serotype was 19A, representing 27% of the isolates.

Conclusions:
Of the vaccine eligible IPD cases in children under 5, almost half (~46%) were age appropriately vaccinated with PCV7. Despite low PCV7 coverage, serotypes of only 4/41 cases were PCV7 serotypes. Serotype 19A is responsible for the largest proportion of IPD in Oklahoma children under 5, which may parallel a documented increase in non-vaccine serotypes in the US.