Determination of Nasopharyngeal Carriage of Streptococcus pneumoniae and Response to the Pneumococcal Polysaccharide Vaccine in Children with Recurrent Infections

Nasopharyngeal carriage of Streptococcus pneumoniae in asymptomatic patients plays an essential role in pneumococcal transmission and generally precedes invasive pneumococcal disease (IPD). The influence of nasopharyngeal pneumococcal carriage on antibody response to pneumococcal vaccine has not been well defined.

Objective: To study the impact of the nasopharyngeal carriage of pneumococcus on the antibody response to pneumococcal polysaccharide vaccine in a pediatric group.

Methods: Prospective study that included 20 pediatric patients with recurrent respiratory infections from an outpatient Immunology clinic in Santiago (Chile). All patients underwent a previous immunological study. The nasopharyngeal carriage of Streptococcus pneumoniae was investigated in a nasal and pharyngeal swab sample, and bacteriological culture and serotyping were performed for 10 pneumococcal serotypes. At the inclusion visit, all children received 23-valent pneumococcal polysaccharide vaccine (Pneumo-23®, Sanofi Pasteur). Pneumococcal anti-polysaccharide IgG class antibodies for 10 serotypes were measured in a blood sample at study entry, at 45-60 days and at 12 months after vaccination. The groups were compared according to nasopharyngeal carriage and antibody response to the vaccine.

Results: Ten patients had nasopharyngeal carriage (5 women, mean age 9, range 4-14 years) (group 1) and 10 patients did not carry the pneumococcus (group 2 control). The isolated serotypes (S) were S1 = 4, S5 = 3, S6B, S14 and S19A, one each. There were no differences in IgG levels before vaccination between the group with nasopharyngeal carriage of pneumococcus with respect to the group that did not carry pneumococcus in any of the 10 serotypes evaluated. In contrast, specific IgG levels were significantly higher for S1 (p <0.05), S5 (p <0.05) and S9 (p <0.02) at 45-60 days post vaccination and for S1 (p<0.05) and for S5 (p<0.05) at 12 months post-vaccination in the groupwith positive carriage of pneumococcus in nasopharyngeal secretion compared to group 2.

Conclusions: In this series of children older than 4 years with recurrent respiratory infections without immunodeficiencies, nasopharyngeal carriage of Streptococcus pneumonia did not affect the IgG antibody response induced by the 23-valent pneumococcal polysaccharide vaccine. Carriage was detected in 50% of the included cases and the most frequent serotypes isolated were S1 and S5. It is likely that the carriage of these two serotypes has a favorable effect on a better response to the vaccine.