High proportion of pregnant women and migrants among adults hospitalised with varicella in Belgium 2012-2022: a case series study

OBJECTIVES: To describe the characteristics and outcomes of adults hospitalised with varicella in Belgium, where universal varicella vaccination is not offered in children and to identify implications for targeted vaccination strategies. METHODS: A retrospective study was conducted in three Belgian hospitals during a 10-year period (2012-2022), including adults hospitalised >24 h with varicella or varicella pneumonia, identified through microbiological results and minimal clinical datasets. Demographic, clinical, and outcome data were analysed. RESULTS: Among 74 hospitalised adults, 13 (17.6%) had varicella pneumonia. Most patients were male migrants living in precarious conditions, and a substantial proportion were undocumented. Pregnant women accounted for a quarter of admissions, and many reported recent contacts with a child with varicella. Most patients received antiviral therapy and had favourable outcomes; one death occurred in an immunocompromised patient. A notable fraction of cases would have been missed by routine surveillance relying on minimal clinical data alone. CONCLUSIONS: In the three studied hospitals, adult hospitalisations caused by varicella cluster in socially vulnerable groups and pregnant women. Varicella vaccination for newly arrived refugees and systematic identification and vaccination of seronegative women of childbearing age could reduce the burden of varicella hospitalisations.