Pneumococcal vaccine in sickle cell disease: IgG and IgM antibody response

Infection with Streptococcus pneumoniae after immunization with polyvalent pneumococcal polysaccharide vaccine has been reported recently in some patients with sickle cell disease (SCD). Since previous studies have suggested that patients with functional hyposplenia may not be able to produce normal levels of protective antibody and/or to switch from IgM to IgG class of antibody in response to some forms of antigenic challenge, we investigated the ability of patients with SCD to form IgM and IgG antibodies after immunization with pneumococcal polysaccharide. Our results demonstrate that both normal individuals and patients with SCD respond with both IgM and IgG antibodies. The level and predominant class of antibody varied with the serotype of antigen tested. Although statistically significant differences were not found, slightly lower responses, especially to pneumococcal polysaccharide type 6, were noted for patients with SCD. Further investigation of the immunoglobulin class of antibody produced by patients with vaccine failure will be necessary to determine if inadequate IgG or IgM response contributes to the lack of protection for these patients.