Safety and Immune Response of a Rabies Vaccine With the Essen Schedule and a Two-Dose Booster

Vaccine

human rabies vaccine (Vero Cell), immunogenicity, safety, Essen regimen

Rabies is caused by rabies virus with a 100% mortality rate in humans. Most of cases occur in Africa and Asia, mainly in underserved populations. Rabies is a vaccine-preventable disease in both humans and animals. Over the years, the Vero cell rabies vaccine has been recognized by the World Health Organization (WHO) and the European Union, and is widely used globally. Currently, one of the post-exposure prophylaxis (PEP) regimens recommended by the World Health Organization (WHO) is the five-dose "Essen" regimen (1-1-1-1-1), involving one intramuscular dose administered on days 0, 3, 7, 14, and 28 respectively. This clinical trial was to assess the immunogenicity and safety of a freeze-dried human rabies vaccine (Vero Cell) in healthy population for the large-scale developing, and explore the booster vaccination.

Rabies is caused by rabies virus with a case fatality rate approaching 100% in humans. Studies reported that about 59000 human deaths and over 3.7 million disability-adjusted life years lost every year. Most of cases occur in Africa and Asia, mainly in underserved populations, with approximately 40% of cases in children aged \<15 years. Fortunately, rabies is a vaccine-preventable disease in both humans and animals. Post-exposure prophylaxis (PEP), is the critical intervention for preventing the onset of the disease. Conventional Vero cell rabies vaccines have been used globally for decades, demonstrating excellent safety and immunogenicity. However, their production typically requires the use of animal-derived components, such as fetal bovine serum or human serum albumin, in the cell culture medium. This practice raises potential concerns regarding the risk of contamination with adventitious agents, batch-to-batch variability, and the potential for allergic reactions. To address these limitations, a new generation of purified Vero rabies vaccine produced in serum-free medium has been developed. This vaccine uses the same Pitman-Moore virus strain as the traditional vaccines but is manufactured without any human or animal serum-derived components, significantly reducing the risk of extraneous protein contamination and representing a substantial advancement in vaccine technology and safety. The shift to a serum-free production process, while a clear advantage for safety, raises critical questions regarding the vaccine's immunogenicity and the duration of protection it confers. This study aims to systematically evaluate the available evidence of the serum-free Vero cell rabies vaccine. First, we will critically assess its immunogenicity in PEP settings. Second, we will assess the long-term persistence of protective antibody titers following primary vaccination. Finally, we will discuss the rationale for and evidence on booster vaccination strategies.

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