Impact of IgM Antibodies on Cross-Protection against Pneumococcal Serogroups 6 and 19 after Immunization with 7-Valent Pneumococcal Conjugate Vaccine in Children

Although it is well known that pneumococcal conjugate vaccines provide cross-protection against some vaccine-related serotypes, these mechanisms are still unclear. This study was performed to investigate the role of cross-protective IgM antibodies against vaccine-related serotypes 6A, 6C, and 19A induced in children aged 12-23 months after immunization with 7-valent pneumococcal conjugate vaccine (PCV7). We obtained serum samples from 18 Korean children aged 12-23 months after a PCV7 booster immunization. The serum IgG and IgM concentrations of serotypes 6B and 19F were measured by enzyme-linked immunosorbent assay (ELISA) in serum. The opsonic indices (OIs) against vaccine serotypes 6B and 19F and vaccine-related serotypes 6A, 6C, and 19A were determined by an opsonophagocytic killing assay (OPA) in IgM-depleted and control serum. Both IgG and IgM antibodies in ELISA and opsonic indices in OPA against serotypes 6B and 19F were demonstrated in the immune serum. IgM depletion decreased the OIs against vaccine serotypes 6B (geometric means of OIs (GMIs) of 3,009 vs. 1,396, 38% reduction) and 19F (1,117 vs. 750, 36% reduction). In addition, IgM depletion markedly decreased the OIs against vaccine-related serotypes 6A (GMIs of 961 vs. 329, 70% reduction), 6C (432 vs. 185, 72% reduction), and 19A (301 vs. 166, 58% reduction). The booster immunization PCV7 induced protective antibodies in the form of both IgG and IgM isotypes. IgM antibodies contributed to eliciting cross-protection against vaccine-related serotypes as well as against vaccine serotypes.

The Association between Asthma and Invasive Pneumococcal Disease: A Nationwide Study in Korea

The purpose of this study was to investigate the association between asthma and invasive pneumococcal disease (IPD) in Korea. A retrospective population-based cohort study was conducted using the Korean Health Insurance Review and Assessment database 2010-2011. The subjects included 935,106 (2010) and 952,295 (2011), of whom 398 (2010) and 428 (2011) patients with IPD were identified. There was significant difference in the prevalence of IPD in patients with and without asthma (0.07% vs. 0.02% in 2010 and 0.08% vs. 0.01% in 2011; P<0.001). After adjusting for age and gender, patients with asthma showed over a three-fold increased risk of IPD compared with patients without asthma (adjusted odds ratio [aOR] 3.90, 95% confidence interval [CI] 3.02-5.03 in 2010 / aOR, 5.44; 95% CI, 4.10-7.22 in 2011; P<0.001). These findings were also significant in children (aOR, 2.08; 95% CI, 1.25-3.45 in 2010; P=0.005 / aOR, 3.26; 95% CI, 1.74-6.11 in 2011; P<0.001). Although diabetes mellitus was also significantly associated with IPD, relatively low ORs compared with those of asthma were noted (aOR, 1.85; 95% CI, 1.35-2.54 in 2010 / aOR, 2.40; 95% CI, 1.78-3.24 in 2011; P<0.001). Both children and adults with asthma are at increased risk of developing IPD.