Meningococcal C Polysaccharide Vaccine Induces Immunologic Hyporesponsiveness in Adults: Additional Data

To the Editor—Richmond et al. [1] reported that the immune response to meningococcal polysaccharide vaccine (MPV) for serogroup C is suppressed in adults who have been previously immunized with the vaccine. The immune response to MPV for serogroup C has been shown to be suppressed in children !2 years old who had received a primary series of this vaccine [2, 3]. However, the vaccine is not licensed for children !2 years old and should not be used for this age group except under special circumstances, such as an outbreak setting [4]. There are no data published that investigate this phenomenon in adults who have received successive doses of MPV at both the recommended dose and at the recommended interval (3–5 years) for revaccination [4]. The opportunity to investigate this issue exists at Aventis Pasteur, since all employees who enter the manufacturing site for MPV are required to receive MPV at the recommended dose every 3–5 years. We evaluated serum antibody responses to serogroup C for 51 consecutive individuals who had received a booster dose of quadrivalent MPV (Menomune-A/C/Y/W-135) ∼5 years after either 1 dose (13 individuals) or 2 successive doses (38 individuals) at an interval of ∼5 years (table 1). The antibody concentration was determined by an ELISA [5] done on serum samples collected just prior to immunization and ∼28 days after immunization. The results showed a pre–booster vaccination level of IgG against serogroup C of 7.8 mg/mL and a post–booster vaccination level of 17.3 mg/mL ( ). ReP p .006 sults also showed a pre–booster vaccination level of IgM of 0.48 mg/mL and a post–booster vaccination level of 1.6 mg/mL ( ). These responses represent 2.2-fold and 3.4-fold inP ! .001 creases for IgG and IgM, respectively. In addition, an IgG antibody concentration of 11 mg/mL was present in 94% of persons both before and after they had received a booster vaccine. An IgG antibody concentration 12 mg/mL was present in 86% of persons before they had received a booster vaccine and in 94% after the booster vaccine. These data demonstrate that a substantial and significant polyclonal immune response to serogroup C occurs after a booster dose in individuals who had received 1 or 2 prior doses of MPV at the recommended interval.