Rabies immunoglobulin utilization and delayed presentation following category III rabies exposure: a 10-year retrospective study in Hangzhou, China

Background Rabies is an almost invariably fatal, vaccine-preventable zoonosis. Rabies immunoglobulin (RIG) is recommended for Category III exposures, yet real-world RIG utilization remains poorly characterized. This study examined temporal trends and factors associated with RIG utilization and delayed presentation among Category III exposure patients in China. Methods A retrospective study was conducted using clinical records of Category III exposure patients presenting to a high-volume rabies prevention clinic in Hangzhou, China, from 2015 to 2024. Calendar year 2018 was treated as a temporal reference year for descriptive comparison. Multivariable logistic regression identified factors associated with RIG non-administration and delayed presentation (>24 h post-exposure). Results A total of 14,270 eligible cases were analyzed. Overall RIG utilization was 37.54%, declining from 53.09% in 2015 to 7.14% in 2022. RIG non-administration was independently associated with male sex (OR 1.20, 95% CI 1.11–1.29), age 18–59 years (OR 3.25, 95% CI 2.95–3.59), exposure at home (OR 1.47, 95% CI 1.33–1.63), presentation in 2018 (OR 2.38, 95% CI 2.01–2.82) and in 2019–2024 (OR 4.49, 95% CI 3.96–5.09), and delayed presentation (OR 1.43, 95% CI 1.32–1.55). The overall delayed presentation rate was 34.47%; independent risk factors included age 18–59 years (OR 1.37, 95% CI 1.24–1.52), exposure at home (OR 1.57, 95% CI 1.41–1.74), and presentation in 2018 (OR 1.61, 95% CI 1.40–1.86) and in 2019–2024 (OR 1.77, 95% CI 1.62–1.94). Conclusion RIG utilization was low and showed marked temporal variation during 2015–2024, and one third of patients presented more than 24 h after exposure. Both outcomes were concentrated among working-age adults and domestic exposure settings. These findings describe service utilization patterns and identify subgroups in which gaps in PEP delivery are concentrated; targeted risk communication and routine monitoring of RIG utilization and presentation timeliness are needed.