Rabies remains an important cause of death, fear, and economic disruption in many regions of the world. Around 1.5 million people are treated for exposure each year, and approximately 59 000 die. Around 95% of human cases occur in Asia and Africa, mostly affecting children in poor rural communities.
Currently approved human vaccines requires several doses to be effective and are too expensive for mass vaccination programmes in rabies endemic regions. They are instead used as pre-exposure prophylaxis in some high risk groups, and as part of post-exposure prophylaxis alongside anti-rabies immunoglobulin. The majority of post-exposure treatment cost are born by patients and their families in poor communities.
Exposure to rabies is most commonly through being bitten by an infected animal, usually a dog. Given the high costs of human vaccines, control of rabies is currently most economically viable through the vaccination and control of dog populations. Such control has become a focus of WHO-led eradication efforts. The high turn over and mobility of dog populations in many areas makes such control difficult to achieve, and even more difficult to sustain in the long term.
A cheap, easy to use rabies vaccine for humans that could be used in mass vaccination campaigns would be a valuable weapon in the battle against rabies.
We have developed a novel rabies vaccine based on an adenovirus vector. The vector is unable to replicate in mammalian cells, but results in a protective immune response against the rabies virus. The vector is based on a chimpanzee adenovirus strain, removing the risks associated with pre-existing immunity to the vector in humans.
In a non-human primate trial, this novel rabies vaccine outperformed a currently licenced vaccine: a single dose protected 100% of animals when exposed to rabies 22 months after vaccination. We are currently working to translate this pre-clinical success into a vaccine for human use. We are developing this vaccine for production at the Clinical Bio-Manufacturing Facility for a Phase I safety trial in adult volunteers.
Cost estimates suggest this vaccine could be produced for less than US$4 a dose at scale, making it significantly cheaper than current rabies vaccines and economical to use for large-scale pre-exposure prophylaxis.
Alongside this work, we are also developing a thermostabilisation method to limit the need for cold-chain storage. This process would add around US$1 per vaccine dose, making it an inexpensive way of protecting vaccine supplies, especially in remote areas. Further information on this work is available here. A thermostabilised preparation of this rabies vaccine will also be included in the upcoming Phase I trial.