Impact of routine immunization using meningococcal C conjugate vaccine on invasive meningococcal disease in British Columbia.

OBJECTIVES

(1) To examine trends in serogroup-specific invasive meningococcal disease (IMD) incidence associated with the protein-polysaccharide conjugate C vaccine (MCC) program in BC; (2) To assess for evidence of capsule switching and serogroup replacement; (3) To discuss whether recent data support modification of the current MCC program to include the quadrivalent protein-polysaccharide conjugate vaccine (MCV-4).

METHODS

Information on IMD cases since 1998 were extracted from surveillance databases. Annual IMD incidence rates and corresponding three-year moving averages were calculated. Data management was performed using Microsoft Office Excel 2003. Time trends were analyzed using chi-square test for linear trend.

RESULTS

For 2003-2006, no significant trends were found in rates of serogroup-specific or total IMD in the overall BC population. Among children <18 years, average annual incidence of serogroup-C IMD has declined with a downward trend (p=0.05). Median age of serogroup-C IMD increased from 16 years (2003) to 42 years (2006). No significant change in incidence rates of pediatric IMD from any non-C serogroup was detected.

DISCUSSION: We document a decreasing trend of pediatric serogroup-C IMD and an increase in median age of serogroup-C IMD cases since 2003, most likely explained by protection from immunization. While the proportion of serogroup-Y IMD has increased, incidence rates of non-C vaccine-preventable IMD have not increased in BC. While incorporation of MCV-4 in routine childhood immunization is desirable to address the few residual cases of non-C vaccine-preventable IMD, it would take several decades to appreciate a benefit from a modified childhood program.