Evidence for familial immune defect in meningococcal meningitis.

Twenty-six patients who had recovered from group A meningococcal meningitis were vaccinated with group C meningococcal polysaccharide and tetanus toxoid. Their haemagglutinating antibody response was measured two weeks later and compared with those of 22 siblings and 39 controls. Patients and siblings had a significantly lower antibody response to the group C vaccine but not to tetanus toxoid. This suggests that patients susceptible to meningococcal disease may have an immune defect involving their response to meningococcal polysaccharides.