Antibody response to purified pneumococcal polysaccharides was studied in 36 splenectomized children with β-thalassemia. All children were vaccinated against Pneumococcus (pneumo-23, Pasteur Merieux) before splenectomy and booster dose five years and more later. Serologic examination for specific antibody levels for pneumococcal polysaccharides was performed immediately before revaccination and three weeks after.

Measurement of protective antibody levels to pneumococcal capsular polysaccharides was performed by ELISA, established in our lab, after absorption of the sera with cell wall polysaccharide in order to detect the real protective antibody levels against pneumococcus.

Twenty nine out of thirty six (29/36, 80%) patients had no antibodies and responded with high levels after booster. Five children (5/36, 14%) had sufficient antibody levels before booster with a subsequent enhancement after revaccination. Finally two children (2/36, 6%) had no detectable antibody levels either before and after booster.

We conclude that children with β-thalassemia and splenectomy have good antibody response to Pneumo-23, as indicated from elevation of antibodies after revaccination. As most of them had no protective titres of antibodies before revaccination, close follow up of antibodies is indicated to define the appropriate time of revaccination. Children who had no response to Pneumococcus may have a deficiency in producting specific antibodies against polysaccharide antigens and perhaps vaccination with a protein conjugated vaccine may induce antibody response.