Haemophilus influenzae type B (Hib) necrotizing soft tissue infection (NSTI) in a vaccinated 16-month-old Inuit boy: a case report.

Necrotizing soft tissue infection (NSTI) caused by Haemophilus influenzae type B (Hib) is rare and life-threatening. We report severe monomicrobial Hib NSTI in a 16-month-old Inuit child who had received 3 doses of the Hib vaccine, highlighting vaccine failure and host susceptibility. The child sustained a minor fall to the left thigh without skin breakdown and developed fever the same day, initially treated with amoxicillin for presumed acute otitis media. He re-presented with persistent fever, progressive leg pain, swelling, ecchymosis, and refusal to weight-bear, prompting air transfer to the regional hospital and the initiation of ceftriaxone. Investigations showed C-reactive protein >90 mg/L, a white blood cell count of 13.6 ×10⁹/L, normal creatine kinase, and unremarkable radiographs. Owing to concern for necrotizing infection, the patient was transferred to a tertiary pediatric intensive care unit. Antimicrobials were escalated to piperacillin-tazobactam, vancomycin, and clindamycin, and intravenous immunoglobulin was administered. Emergent surgical debridement demonstrated extensive dermal and subcutaneous necrosis with preserved fascia and muscle. Blood and tissue cultures grew Hib. He required mechanical ventilation, inotropic support, and multiple additional debridements prior to skin grafting. Household contacts received chemoprophylaxis. Immunologic evaluation was unremarkable; genetic testing was non-diagnostic. NSTI requires prompt recognition, surgical debridement, and targeted antimicrobial therapy. While most cases are due to group A Streptococcus or polymicrobial infections, Hib is rare, with few pediatric cases reported. Vaccine failures occur, particularly before the 18-month booster, reflecting waning immunity. Indigenous populations remain disproportionately affected. Invasive Hib disease despite vaccination warrants evaluation for underlying immunodeficiency. Invasive Hib infection should be considered even in fully vaccinated children. Continued surveillance, prompt surgical management, public health response and investigations of host susceptibility remain essential.