Specific antibody deficiency

• Failure to respond to an unconjugated polysaccharide vaccine despite otherwise normal immune evaluation
• Characterized by recurrent community-acquired pneumonia
• Investigated by giving pneumococcal 23-valent polysaccharide vaccine and measuring titres 4 to 6 weeks later
  • Serotype specific titres should be ≥1.3 μg/mL or 2-fold increase; if not, it suggests specific antibody deficiency
• Management is immunization with the conjugated 13-valent pneumococcal vaccine