[Extensive swelling reaction after a pentavalent vaccination].

Area of Science:

• Pediatrics
• Immunology
• Vaccinology

Background:

• Injection site reactions (ISRs) are local adverse drug reactions following vaccination.
• The diphtheria, tetanus, acellular pertussis, inactivated poliomyelitis, Haemophilus influenza type b (DTPCa-Hib) vaccine is commonly administered via intramuscular injection.
• Understanding ISRs is crucial for vaccine safety monitoring.

Observation:

• A 3-year-old boy presented with fever 24 hours post-DTPCa-Hib vaccination in the deltoid muscle.
• Rapid, extensive, pain-free redness and swelling of the limb developed.
• Initial treatment for suspected cellulitis was administered.

Findings:

• The patient experienced rapid improvement within 12 hours, with fever resolution and decreased limb swelling.
• A diagnosis of injection site reaction (ISR) was confirmed due to the rapid recovery and absence of other anomalies.
• Extensive limb swelling is a known, frequent ISR, particularly after the fourth DTPCa-Hib dose.

Implications:

• Deltoid muscle administration in children under 3 may increase ISR risk compared to thigh injections.
• Acellular pertussis components might be associated with a higher ISR incidence.
• ISRs are typically self-limiting and do not contraindicate future vaccinations.