First-in-Human Trial of mRNA Rabies Vaccine
Overview of the Study
In a groundbreaking first-in-human trial, researchers aimed to evaluate the safety and efficacy of a prophylactic mRNA rabies vaccine. The potential success of this study could pave the way for advancements in vaccine technology, enabling more effective responses to emerging pandemic threats. Traditional vaccine methods often rely on live or attenuated viruses to combat infectious diseases, highlighting the need for faster and more cost-effective vaccine production.
Benefits of mRNA Vaccine Technology
mRNA vaccine technology offers a solution with reduced production costs and expedited manufacturing processes. Previous animal studies have shown that mRNA from vaccines effectively enters immune cells, prompting an immune response. The primary goal of this proof-of-concept trial was to evaluate the safety and immunogenicity of the mRNA rabies vaccine in healthy human participants.
Assessing Safety and Efficacy
Study Findings
Martin Alberer and his team shared their findings in The Lancet, detailing the safety data collected from 101 participants who received a total of 306 vaccinations. Blood samples were collected from all but one participant, facilitating a comprehensive analysis of the vaccine’s efficacy. Participants were divided into various treatment groups, testing different doses (ranging from 80 to 640 micrograms), dosing schedules (both long and short), routes of administration (intradermal and intramuscular), and injection techniques (needle-syringe and needle-free device).
The results revealed significant differences in immune responses between the two administration methods. No antibody responses were observed in participants who received intramuscular vaccinations via needle-syringe. In contrast, 10 out of 13 participants who were vaccinated with the intramuscular injector device exhibited virus neutralizing titres, with 5 achieving the WHO-specified protective antibody titre of 0.5 international units per milliliter. Among those receiving intradermal vaccinations with a needle-syringe, only one participant from the highest-dose group demonstrated a minimal antibody response. Conversely, 40 out of 45 participants receiving intradermal vaccinations via the injector device developed antibodies, with 32 reaching the WHO threshold.
Side Effects and Safety Profile
Safety Observations
The safety profile of the mRNA rabies vaccine candidate closely resembles that of traditional vaccines and is largely associated with immune system stimulation. Most participants reported mild to moderate local irritations and systemic side effects, such as headaches, fever, and chills, all of which resolved promptly. A few serious side effects were recorded, including one case of transient Bell’s palsy, another involving a nasal septum deviation that required surgery, and one case of campylobacter infection. Fortunately, all serious adverse events resolved without lasting consequences.
Conclusion and Future Directions
This trial marks a significant milestone as the first attempt to assess mRNA vaccinations against infectious diseases in humans. The mRNA rabies vaccine has demonstrated safety and efficacy in both animal and human studies. However, further improvements are necessary to enhance the vaccine’s immunogenicity, aiming for 100% of vaccinated individuals to achieve the WHO-recommended virus neutralizing titre levels. Continued research is essential, as an optimized model could facilitate the development of vaccines targeting other potentially fatal infectious diseases.
Reference
Alberer M, Gnad-Vogt U, Hong HS, et al. Safety and immunogenicity of a mRNA rabies vaccine in healthy adults: an open-label, non-randomised, prospective, first-in-human phase 1 clinical trial. The Lancet. 2017.