Paediatric mpox during Sierra Leone’s 2024 to 2025 clade IIb outbreak: A national surveillance and outbreak-investigation study of 415 children

Background Evidence on paediatric mpox during contemporary African clade IIb outbreaks remains limited. We described paediatric cases in Sierra Leone’s 2024–2025 clade IIb G.1 outbreak by person, time, and place and examined clinical care, outcomes, vaccination records, and documented exposures. Methodology/Principal findings We conducted a retrospective descriptive study using the national District Health Information Software 2 (DHIS2) mpox database, supplemented by patient charts and outbreak-investigation forms. Among 5,466 cases with recorded age, 415 (7.6%) were children younger than 15 years; 188 (45.3%) were aged 0–4 years, 121 (29.2%) were aged 5–9 years, and 106 (25.5%) were aged 10–14 years. Of 415 paediatric cases, 411 were laboratory-confirmed. Outcome was recorded for 261 children; three died (1.1%, exact 95% CI 0.2 to 3.3). Care location was recorded for 285 children; 216 (75.8%) received hospital care for isolation, clinical management, or both. Three sporadic paediatric cases of mpox-like illness were reported from 2017 through 2024; notifications then rose rapidly from April 2025 and peaked in May. Western Area Urban accounted for 195/413 cases with known district; crude notified paediatric rates were highest in Western Area Urban, Koinadugu, and Falaba. Household or caregiving contact was the most common documented exposure among 246 classifiable investigation forms (141, 57.3%). Mpox vaccination status was recorded for 27/54 cases aged 12–14 years; six were vaccinated. Conclusions/Significance Children were not spared during Sierra Leone’s clade IIb outbreak. Response plans should include children in case finding, contact follow-up, clinical care, and vaccination assessment. DHIS2 should capture epidemiologic links, clinical outcomes, vaccine eligibility and status, and potential exposure settings through standardised fields.