Response to pneumococcal conjugate and polysaccharide vaccination in children with rheumatic disease

Children with rheumatic disease and compromised immune system have an increased risk of infection. Streptococcus pneumoniae is a frequent pathogen, and immunization is recommended. In this study, we investigated whether immunocompromised children with rheumatic disease do respond to pneumococcal immunization with 13-valent pneumococcal conjugate vaccine followed by 23-valent pneumococcal polysaccharide vaccine. The study was conducted at two tertiary referral hospitals in Denmark from 2015 to 2018. Patients with rheumatic disease and compromised immune system aged 2-19 years were eligible. Patients were vaccinated with 13-valent pneumococcal conjugate vaccine followed by 23-valent pneumococcal polysaccharide vaccine. A blood sample was collected before vaccination and after each vaccination. IgG antibodies were quantified for twelve serotypes. Seroprotection for each serotype was defined as IgG ≥0.35 µg/mL. A total of 27 patients were enrolled. After the conjugate vaccine, an increase in antibody titres compared with pre-vaccination was found for all serotypes and 9/12 were significant. After the polysaccharide vaccine, the antibody titres for all serotypes but one was seen to increase but none reached significance. The proportion of patients protected before immunization ranged from 20.8% to 100% for the individual serotypes. Odds ratio for achieving seroprotection after the conjugate vaccine was >1 for 10/12 serotypes but only significant for three serotypes. After the polysaccharide vaccine, the odds ratio was >1 for 9/12 serotypes but none reached significance. In conclusion, children with rheumatic disease and compromised immune system respond to pneumococcal immunization with 13-valent pneumococcal conjugate vaccine and maintain antibody levels upon subsequent immunization with 23-valent pneumococcal polysaccharide vaccine.