Objective: to investigate the safety and immunogenicity of 23-valent polysaccharide pneumococcal vaccine (PPV-23) in patients with systemic lupus erythematosus (SLE). Subjects and methods. The investigation enrolled 30 patients with a reliable diagnosis of SLE; of them there were 27 women and 3 men at the age of 19 to 62 years. The disease duration ranged from 9 months to 20 years. At the time of inclusion in the investigation, the disease activity was high in 2 patients, moderate in 3, and low in 20; five patients were in remission. During a year before vaccination, pneumonia was detected in 5 (16.7%) of the 30 patients; there were a total of 18 episodes of various respiratory and ENT infections. The patients were examined at baseline and at 1, 3 and 12 months after vaccination. Standard clinical and laboratory studies and a detailed blood immunological analysis were carried out at visits. The levels of IgG antibodies to capsular polysaccharide pneumococcus were determined during each visit. Twenty-nine patients received glucocorticoids (GCs) at a dose of 5–30 mg/day; 24 – hydroxychloroquine; 14 – cytostatics (CS); 10 – biological agents (BAs) (5 – rituximab, 5 – belimumab). A single dose of 0.5 ml of PPV-23 (Pneumo 23, Aventis) was subcutaneously injected into the upper outer arm. Vaccination was done during the ongoing therapy with GC/CS and belimumab, as well as at least 1 month before the first (next) administration and/or 4.5–5 months after the last rituximab infusion. Results and discussion. 60% of patients were observed to have mild and moderate standard local vaccine reactions; 1 (3.3%) patient had a local hyperergic reaction eliminated within 7 days of the local application of antihistamines and GCs. During the follow-up, there was no SLE exacerbation significantly associated with the vaccination performed. No new autoimmune phenomena were found in any of the cases. A year after vaccination, a significant (2-fold or more) increase in anti-pneumococcal antibody levels remained in 19 (63.3%) patients (respondents); 36.7% of patients were nonrespondents. Among the patients who received a BA, the non-responders were significantly more than among those who did not take the drug (7 (70%) and 4 (20%), respectively) (p = 0.01). When treated with rituximab and belimumab, the number of non-respondents was comparable (4 and 3, respectively). The immunogenicity of PPV-23 was independent of the degree of SLE activity: the vaccine response was absent in 1 out of the 5 patients with high (n = 2) and medium (n = 3) SLE activities, as well as in 10 out of the 25 patients with low disease activity and remission. There was no development of considerable adverse reactions after vaccination in patients with high and medium SLE activity. The overall clinical efficiency of vaccination was 93.3%. Conclusion. Thus, PPV-23 shows a good tolerability and a sufficient immunogenicity in patients with SLE. There is a need for further investigations conducted in large samples of patients during long-term follow-ups in order to more fully evaluate the clinical efficacy, tolerability, and immunogenicity of PPV-23.