Of 45 Russian patients with late complement component deficiency (LCCD) who experienced one to five meningococcal infections, 31 were immunised with a meningococcal A/C/W135/Y polysaccharide vaccine and were followed for 3-8 years. Total and immunoglobulin (Ig) class specific concentration of antibodies to meningococcal polysaccharides in sera of LCCD patients increased significantly 1 month after vaccination and remained elevated for 3 years. Revaccination of LCCD patients 3 years after the first dose restored the total Ig concentrations to those observed 1 year after the first vaccination. Six new episodes of meningococcal infection in four patients developed in the group of 31 vaccinees; six episodes in six patients developed in the same time in the group of 14 non-vaccinated LCCD persons. Survival analysis demonstrated the risk to contract meningococcal disease decreased significantly for vaccinees in comparison to non-vaccinees (P\textless0.05). Vaccination with of meningococcal tetravalent polysaccharide vaccine decreases the risk of meningococcal infection in LCCD patients.