Meningococcal group C conjugate vaccines

Immune response to conjugated meningococcal C vaccine in pediatric oncology patients

BACKGROUND

Following outbreaks of meningococcal disease in Quebec in 1991-1993 and 2000-2001, a mass vaccination campaign was performed. In 2001-2002, children aged 2 months to 20 years were immunized with the Meningococcal CRM197 vaccine (Menjugate). We examined the response of pediatric oncology patients during or following maintenance chemotherapy and post-bone-marrow transplantation to Meningococcal C vaccine.

PROCEDURE

This was an open label descriptive study of a cohort of patients from the oncology clinic at the Montreal Children's Hospital. A positive vaccine response was defined as a fourfold increase in specific IgG from baseline and a bactericidal assay using human complement (hBCA) titer >1:4.

RESULTS

Of the 25 patients with ALL, 13 had a serologic response (average 60-fold increase). The serologic responders had a higher mean B cell count (0.262) compared to non-responders 0.068 x 10.9/L [t(23) = 2.843 (P < 0.05)]. Eleven of the 12 non-responders and 4 of the responders were on maintenance chemotherapy. In addition, two of the five patients post-bone-marrow transplant, responded. Fifteen of the 34 patients (44%) had an adequate hBCA response (mean titer 61). The group included 14/18 serologic responders with hBCA response (P < 0.001) and 16/17 non-serologic responders with no hBCA response (P < 0.001).

CONCLUSIONS

Meningococcal C-conjugate vaccine produced variable responses in children with common cancers. Proximity to chemotherapy and total B cell number may help predict likelihood of response.

The immunopathogenesis of meningococcal disease

This review describes the mechanisms of the immune response to meningococcal disease, examining the extent to which individual variation of the immune response can determine susceptibility. It concludes by summarising the difficulties encountered by recent efforts to develop new immunomodulatory treatments.

The meningococcus tamed?

Serogroup B Neisseria meningitidis is a frequent cause of invasive meningococcal disease, yet there are no effective vaccines suitable for routine immunisation. Limited efficacy has been shown with meningococcal outer membrane vacccines in children 4 years and older. Here we review the status of current research and consider new approaches to development of meningococcal serogroup B vaccines.

Meningococcal disease and travel

Invasive meningococcal disease, in both endemic and epidemic forms, is the cause of significant morbidity and mortality worldwide. Despite all advances in therapy, the fatality rate of meningococcal meningitis remains unacceptably high, between 5% and 10%, and a similar proportion suffers long-term neurological sequalae. Prevention of this rapidly fatal disease is of paramount importance. The use of the available internationally licensed meningococcal vaccines would be indicated for individuals with medical conditions that increase the risk of the disease and for travelers to high-risk countries. In the last 2 years, there has been a shift in the epidemic pattern of meningococcal disease during the Hajj (pilgrimage) season, with predominance of Neisseria meningitidis serogroup W135. Recent changes have been made in the policy issued by the Saudi Ministry of Health (Riyadh, Saudi Arabia), which requires visitors from all over the world arriving for purposes of umra and Hajj to show evidence of vaccination against meningitis with the quadrivalent meningococcal vaccine.

Meningococcal disease: treatment and prevention

Many countries have been experiencing a significant increase in meningococcal disease. With the strains currently circulating, septicaemia is now a more frequent manifestation than meningitis and early recognition of disease manifestations by patient, parent or physician as well as early recognition of disease severity are the most important factors in attempting to reduce mortality and morbidity. Ceftriaxone is the treatment of choice but must be accompanied by aggressive supportive therapy in those with severe disease. The role of steroids is unknown. The evidence to support their use in both meningitis and severe systemic sepsis is discussed. The purified polysaccharide vaccines that have been available for some years may play a limited role in disease prevention. The recently introduced conjugate vaccine for preventing serogroup C disease represents a major advance but no vaccine is currently available to prevent serogroup B disease, cases of which will continue to challenge clinical practice.