Hereditary complement deficiencies are relatively rare worldwide, they account for about 1-10% of primary immunodeficiencies. Acquired complement deficiencies are more prevalent and with the more frequent use of complement inhibitor therapy, the incidence of patients with iatrogenic complement deficiency is increasing. Alike in the inherited forms, patients have a high risk of severe and life-threatening infections caused by encapsulated bacteria (sepsis, meningitis). The most frequent pathogens are Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae. C5 and C3 complement inhibitor therapies are available in Hungary, which are mostly indicated in the treatment of paroxysmal nocturnal hemoglobinuria, myasthenia gravis, neuromyelitis optica and atypical haemolytic uremic syndrome. It is of utmost importance to prevent severe, potentially life-threatening bacterial infections in this group of patients. Nevertheless, there is no Hungarian guidance to decrease the risk of infections, preventive measures are incomplete and not standardized posing potential risk of infections for these patients, so far. In this review, we aim to summarize the international clinical practices and guidance on the infection prevention in complement deficient patients. This recommendation might be a source of an evidence-based Hungarian guideline regarding vaccination and antibiotic prophylaxis in this specifically vulnerable group of patients. Orv Hetil. 2023; 164(25): 971-980.