Comparison of safety and immunogenicity of purified chick embryo cell vaccine using Zagreb and Essen regimens in patients with category II exposure in China

The aim was to compare the safety and immunogenicity of purified chick embryo cell vaccine (PCECV) with Zagreb 2-1-1 and Essen 1-1-1-1-1 regimens in patients with WHO category II exposure in China. Side effects including systemic and local symptoms were recorded for all patients during vaccination with purified chick embryo cell vaccine (PCECV) under Zagreb 2-1-1 or Essen 1-1-1-1-1 regimens, and the rabies neutralization antibody titers in patients' serum at days 0, 7, 14, 45, 365 post-immunization were measured to determine the immunogenicity. Fever and pain were the most common events for systemic and local symptoms respectively, and most side effects (86.78%, 105/121) occurred after the first dose of vaccination. Safety analysis showed differences in side effects in <5-year-old patients between Zagreb and Essen regimens, especially after the first dose of vaccination (P = 0.043). Immunogenicity analysis indicated that Zagreb can achieve higher neutralization antibody titers and a greater seroconversion rate in a shorter time but had less persistence than Essen. When compared with the Essen regimen, the Zagreb regimen had a different immunogenicity in all study subjects, and different safety profile in young children, and a further study with a larger population and longer surveillance is warranted.