Long-term thermal stability of group C meningococcal polysaccharide-tetanus toxoid conjugate vaccine

The stability of vaccines during storage and handling is a prerequisite for optimal potency at the time of immunization. Meningococcal group C conjugate vaccines have been successfully incorporated in mass immunization programs, however, thus far no long-term real-time stability studies of these vaccines have been reported. Stability of de-O-acetylated group C meningococcal polysaccharide coupled to tetanus toxoid (GCMP-TT) was evaluated in real time on the basis of immunogenicity and physiochemical properties. The vaccine is formulated as a 0.5 mL suspension containing 10 mug GCMP conjugated to 10-20 mug of TT adsorbed on 0.5 mg aluminum in saline. The single dose syringes were stored under refrigeration (5 +/- 3 degrees C) and at room temperature (25 +/- 2 degrees C) for up to 42 months and at elevated temperature (40 +/- 2 degrees C) for up to 6 months. At both refrigerated and room temperatures, no time-dependent change in animal potency was detectable through 42 months. After the nine months maximum recommended storage period at room temperature, 96% of the baseline serum bactericidal antibody (SBA) titer was maintained. Time-dependent decreases in SBA level and anti-GCMP-TT IgG level were observed at 40 +/- 2 degrees C. No changes in GCMP-TT adsorption and pH occurred in all the studies. Loss of integrity increased over six months at 40 +/- 2 degrees C (p = 0.004). Free sugar content did not change over 36 months under refrigeration. GCMP-TT retained immunogenicity and physicochemical properties under refrigeration and at room temperature (25 +/- 2 degrees C) for up to 42 months.