LB-13. Serotype-specific immunity and unresponsiveness to 7-valent pneumococcal conjugate vaccine in pediatric patients with invasive pneumococcal disease during the introductory phase of this vaccine to Japan
Session: Poster Abstract Session: Late Breaker Posters
Saturday, October 22, 2011
Room: Poster Hall B1
Background: The Japanese government decided to provide 7-valent pneumococcal conjugate vaccine (PCV7) free of charge to all of children in 2010. The vaccine coverage of PCV7 is continuously increasing and it is now approximately 20% in the whole country of Japan. The WHO working group reported that antibody concentrations of 0.2–0.35 ug/ml correlated best with an opsonophagocytic index(OPI) of 8 , which in turn correlated best with protective efficacy in infants.

Method: Serotype-specific immune status of pediatric patients of invasive pneumococcal disease (IPD) has not been fully investigated. 27 pediatric patients with IPD were examined for the serotype-specific immunoglobulin G (IgG) levels using enzyme-linked immunosorbent assay (ELISA) or OPI using a multiplexed opsonization assay after the episode of infection between June 2009 and March 2011 in Japan. 

Result: The mean age of IPD cases were 25.5 months and male sex was 66.7%. 3 (11.1%) were vaccinated with 23-valent pneumococcal polysaccharide vaccine, 8 (34.8%) were vaccinated with 7-valent pneumococcal conjugate vaccine (PCV7) and 16 (59.3%) were unvaccinated before the episode of IPD. Predominant serotypes causing IPD were serotype 6B (n=12, 44.4%), 19F (n=5,18.5%), 14 (n=4, 14.8%), and 19A (n=3, 11.1%). Of 27 cases, serotype-specific IgG and OPI for the causing serotype were determined in sera from 22 cases (81.5 %) and 20 cases (74.1 %), respectively. While the levels of serotype-specific ELISA IgG widely ranged from 0.19 to 6.53 ug/ml for 22 cases, 17 of 20 cases (85.0 %) of the OPI were below 8. Of 12 IPD cases attributable to 6B serotype, two vaccine failures and 4 breakthrough infections were found. In 7 of 9 cases caused by serotype 6B (77.8%), no response was found in OPK for the serotype 6B after at least one dose of PCV7.

Conclusion:Our present data suggest that the OPI is an accurate indicator of serotype-specific immunity rather than ELISA IgG for pediatric IPD, and a serious concern of the immunogenicity to serotype 6B after vaccination with PCV7 has been raised in children in Japan.

Subject Category: I. Adult and Pediatric Vaccines

Kazunori Oishi, MD, PhD, International Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, Suita, Japan, Tomohiro Oishi, MD, PhD, Department of Pediatrics, Niigata University, Niigata, Japan and Naruhiko Ishiwada, Department of Pediatrics, Chiba University, Chiba, Japan


K. Oishi, None

T. Oishi, None

N. Ishiwada, None

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