Active Surveillance on Safety and Compliance of Freeze-dried Human Rabies Vaccine (Vero Cell) — Jiangsu Province, China, 2023–2024

Abstract

Introduction: Rabies vaccination compliance and safety are critical for post-exposure prophylaxis. This study compared the freeze-dried human rabies vaccine (Vero cell) under 4-dose (Zagreb) and 5-dose (Essen) regimens in real-world settings. Methods: In this open-label, randomized trial across Jiangsu Province, China between 2023 and 2024, 2,000 participants received Zagreb (n=999) or Essen (n=1,001) regimens. Active mobile-app surveillance monitored adverse reactions for 28 days post-vaccination. Compliance was assessed through dropout (discontinuation) and out-of-window administration (delayed dosing). Safety and compliance differences were analyzed using the chi-squared or Fisher’s exact tests. Results: Overall adverse reaction rates were comparable (Zagreb: 2.10%; Essen: 2.70%; P=0.385). Solicited local adverse reactions (pain, induration, swelling, and itching) occurred at rates of 1.50% for Zagreb and 2.10% for Essen. Solicited systemic adverse reactions (fever, diarrhea, and vomiting) were 0.60% for both. Dropout rates were statistically similar (8.51% vs. 8.69%; P=0.884), but Zagreb had significantly fewer out-of-window administrations (8.41% vs. 16.38%; P< 0.001). Compliance factors differed: Zagreb was associated with age/marital status/exposure level; Essen additionally involved education and perceived convenience. Conclusion: Both regimens demonstrated comparable safety profiles. The Zagreb regimen showed significantly superior schedule adherence through reduced out-of-window administrations while maintaining similar dropout rates to the Essen regimen.