The DETECT study aims to demonstrate the importance of detecting SPAD in adult patients with recurrent benign and/or severe unexplained bacterial upper/lower respiratory tract infections. Unlike children in whom the deficit may be transient, long-term strategies are warranted in SPAD adult patients to prevent severe infections and lung disability. Beyond the diagnosis of this still unrecognized PID in adult patients, the investigators want to assess the impact of prophylactic antibiotics or IgRT on infections prevention and on quality of life in adult patients with the most severe clinical phenotypes, recurrent infections with high frequency of antibiotics take and/or recurrent infections with complications like bronchiectasis and/or severe infections requiring hospitalizations.

This multicenter observational prospective study will be conducted in 15 university or general hospitals, mostly centers included in the national network of the reference center CEREDIH. Pulmonologists, clinical immunologists and ENT specialists will be solicited in each center to refer patients for inclusions.

All patients who fulfill eligibility criteria will be tested for anti-pneumococcal polysaccharides (PnPSs) response with the 23-valent pneumococcal (unconjugated) vaccine (PPV23) (V1, Day 0: blood sample anti-PnPS antibodies, and immunization; V2, Day 28-56): blood sample for anti-PnPS antibodies).

If a SPAD would be diagnosed, the investigator will be free to consider prophylactic antibiotics and/or IgRT according to the medical history of the patient (notably in case of persistent infections while using prophylactic antibiotics). The efficiency on infections prevention and the impact on health-related quality of life (HRQoL) will be assessed 12 months after initiation of IgRT or prophylactic antibiotics (Visit 3).

Inclusion Criteria:

• 18 to 65 year old patients
• With a history of recurrent bacterial infections of upper and/or lower respiratory tract for at least 2 years, and fulfilling the specific following criteria:
• Recurrent benign infections currently requiring 6 courses of antibiotics /year or more, or Bilateral bronchiectasis/bronchiolitis (after exclusion of cystic fibrosis and ciliary dyskinesia) AND recurrent benign infections currently requiring 3 courses of antibiotics /year or more or A history of severe upper/lower respiratory tract bacterial infection, and/or invasive infection with Streptococcus pneumonia, Streptococcus pyogenes or Haemophilus influenzae, which required hospitalization in the last 2 years, AND recurrent benign infections currently requiring 3 courses of antibiotics /year.
• Normal serum IgG, IgA, IgM and IgG subclasses levels, normal CH50 and serum complement C3 and C4 proteins levels, normal T cells count
• Normal B cell count, normal serum protein electrophoresis and immunofixation. (* excepted for Pseudomonas aeruginosa colonization)

Exclusion Criteria:

• Any general condition that predisposes to infections: solid or hematological malignancies, diabetes mellitus, severe alcohol or intravenous drug abuse, chronic liver or kidney failure, human immunodeficiency virus infection, anatomic or functional asplenia, drug-induced 1 neutropenia, or solid organ or hematopoietic stem cell transplantation;
• Any local predisposing factor to infections: cigarette smoking (> 10 pack-year and/or 5 cigarettes/day), underlying infection (tuberculosis, influenza…), chronic obstructive pulmonary disease, oral, dental or skin conditions favorizing infections, streptococcal skin infections
• Any other SID or PID diagnosed before inclusion
• Pregnancy
• PPV23 administration in the last 2 years (risk of hyporesponsiveness)

Patients seen in Pneumology, Immunology, ENT or Infectious Diseases departments