Immunoglobulin M and G antibody responses and persistence of these antibodies in adults after vaccination with a combined meningococcal group A and group C polysaccharide vaccine.

Adult volunteers were injected with a combined meningococcal group A and group C polysaccharide vaccine. Immunoglobulin M (IgM) and IgG antibody levels against both polysaccharides were measured in serum samples taken 14 days as well as 3 years after vaccination. For both group A and group C polysaccharides, the IgM and IgG antibody levels at 14 days postvaccination were positively related. The IgM-to-IgG antibody ratio at 14 days postvaccination was an indicator for the persistence of both IgM and IgG antibodies during the next 3 years; a high ratio meant a short persistence, whereas a low ratio was associated with a long persistence.