Mencevax ACWY: A Comprehensive Monograph

Executive Summary

Mencevax ACWY is a quadrivalent meningococcal polysaccharide vaccine designed for active immunization against invasive disease caused by Neisseria meningitidis serogroups A, C, W-135, and Y. As a first-generation unconjugated polysaccharide vaccine, it represented a significant public health tool following its development, providing protection for adults and older children, particularly in high-risk settings such as for travelers to endemic regions and during outbreak control. Its mechanism of action relies on the induction of a T-cell independent immune response, which stimulates the production of serum bactericidal antibodies but fails to generate long-term immunological memory. This fundamental immunological characteristic results in several critical limitations: the vaccine is poorly immunogenic in infants under two years of age, the protection it offers is of short duration (typically 3-5 years), and it does not contribute to herd immunity by reducing nasopharyngeal carriage of the bacteria.