Comparison of Immune Responses to Two Quadrivalent Meningococcal Conjugate Vaccines (CRM197 and Diphtheria Toxoid) in Healthy Adults

Abstract

Background: After the introduction of the meningococcal ACWY-CRM197 conjugate vaccine (MenACWY-CRM) in 2012 and the meningococcal ACWY-diphtheria toxoid conjugate vaccine (MenACWY-DT) in 2014, immunization was recommended for certain high-risk groups including new military recruits in Korea. However, comparative immunogenicity studies for these vaccines have not been performed in Korea. Here, we compared the immunogenicity of these two vaccines in healthy adults.

Methods: A total of 64 adults, 20-49 years of age, were randomly divided into two groups (1:1) to receive either of the two vaccines. The sera were obtained before and 1 month after vaccination and tested for serogroup-specific serum bactericidal activity using baby rabbit complement.

Results: There were no significant differences post-vaccination in the geometric mean indices and the seropositive rate to all serogroups between the vaccines. The proportion of seropositive subjects after vaccination ranged from 88% to 100%.

Conclusion: Both meningococcal conjugate vaccines showed good immunogenicity in healthy Korean adults without statistically significant differences. Further investigations for serotype distribution of circulating meningococci and the immune interference between other diphtheria toxin-containing vaccines concomitantly used for military recruits are needed to optimize immunization policies.

Trial registration: Clinical Research Information Service Identifier: KCT0002460.

Keywords: Adult; Immunogenicity; Meningococcal Vaccines.

Fig. 1. Subject disposition flowchart.

MenACWY-DT = quadrivalent meningococcal diphtheria toxoid conjugate vaccine, MenACWY-CRM = quadrivalent meningococcal CRM197 conjugate vaccine.

Fig. 2. Scatter plot of serum bactericidal indices against serogroups A, C, W-135, and Y at baseline and post-immunization (1 month after). At baseline, MenACWY-DT group, open circle; 1 month after, MenACWY-DT group, closed circle; at baseline, MenACWY-CRM group, open triangle; 1 month after, MenACWY-CRM group, closed triangle; black line, limit of detection based on our assay format.

MenACWY-DT = quadrivalent meningococcal diphtheria toxoid conjugate vaccine, MenACWY-CRM = quadrivalent meningococcal CRM197 conjugate vaccine, LOD = limit of detection, SBI = serum bactericidal index.

Fig. 3. Scatter plots for the serum bactericidal indices at pre-immunization and fold-increases from pre- to post-immunization. Horizontal black line, cut-off of immune response (4-fold increases in serum bactericidal indices from pre- to post-immunization); vertical black line, cut-off of seropositivity for serum bactericidal indices.

MenACWY-DT = quadrivalent meningococcal diphtheria toxoid conjugate vaccine, MenACWY-CRM = quadrivalent meningococcal CRM197 conjugate vaccine, SBI = serum bactericidal index, rho = Spearman correlation coefficient.

Fig. 4. Reverse cumulative distribution curve of serum bactericidal indices against serogroup A, C, W-135, and Y at baseline and post-immunization (1 month after). At baseline, MenACWY-DT group, open circle; 1 month after, DT group, closed circle; at baseline, MenACWY-CRM group, open triangle; 1 month after, closed triangle; vertical black line, limit of detection (8).

MenACWY-DT = quadrivalent meningococcal diphtheria toxoid conjugate vaccine, DT = diphtheria toxoid, MenACWY-CRM = quadrivalent meningococcal CRM197 conjugate vaccine, SBI = serum bactericidal index.