Pediatric Infectious Diseases and Immunization
This domain tests the routine immunisation schedule, vaccine contraindications and catch-up rules, plus recognition and empirical management of common and life-threatening childhood infections. Egyptian items often combine a vaccination history with a clinical scenario and ask what to give next.
Immunisation rules
- Live attenuated vaccines include BCG, oral polio, MMR, varicella and rotavirus. Avoid them in severe immunodeficiency, pregnancy, and within four weeks of another live vaccine (same-day administration is acceptable).
- Inactivated vaccines include DTP, Hib, hepatitis B, IPV, pneumococcal, meningococcal and influenza.
- True contraindications: anaphylaxis to a vaccine component, and encephalopathy within seven days of a pertussis-containing vaccine. Fever, minor illness, breastfeeding, current antibiotics and prematurity are not contraindications.
- Egypt's Expanded Programme on Immunization gives BCG, hepatitis B and oral polio at birth, a pentavalent DTP-hepatitis B-Hib series with oral polio through the first year, and MMR in the second year. Always confirm the current national edition before answering a schedule item.
Fever without focus in the young infant
- Under 3 months with temperature 38 degrees or more: full sepsis evaluation (blood, urine and cerebrospinal fluid), admit, and start ampicillin plus gentamicin or cefotaxime.
- Three to 36 months with high fever and no focus: culture the urine in every child, and consider pneumonia and occult bacteraemia.
Exanthems that are easy to confuse
- Measles: three to four days of cough, coryza and conjunctivitis, Koplik spots, then a descending maculopapular rash.
- Rubella: rash spreading from the face within a day, prominent postauricular and occipital nodes, little fever.
- Roseola: three to five days of high fever followed by a rash as the fever falls (HHV-6).
- Varicella: crops of vesicles at different stages. Scarlet fever: sandpaper rash, strawberry tongue, Pastia lines, treated with penicillin.
CSF interpretation
Bacterial meningitis shows neutrophil predominance, high protein and low glucose (under 40 mg/dL or a CSF-to-serum ratio below 0.4). Neonatal profiles are atypical and may be lymphocytic. Never delay antibiotics for an unstable child awaiting lumbar puncture.
Worked example
A 4-month-old has fever, irritability and a bulging fontanelle; CSF shows 900 white cells with 85% neutrophils, protein 180 mg/dL and glucose 25 mg/dL with a serum glucose of 110 mg/dL. Treat as bacterial meningitis: give dexamethasone with or just before the first antibiotic dose, then cefotaxime plus ampicillin (or vancomycin where pneumococcal resistance is a concern) and admit to intensive care.
Traps
Withholding MMR because of egg allergy (not a contraindication), and treating a febrile child with antibiotics before obtaining cultures.