Could one vaccine protect against both Lassa fever and rabies?
An experimental vaccine against Lassa virus and rabies has shown promise in its first human trial.
- 9 June 2026
- 4 min read
- by Linda Geddes
At a glance
- Researchers tested an experimental vaccine designed to protect against both Lassa fever and rabies in a phase 1 trial in 54 healthy adults in the US.
- The vaccine was found to be safe and triggered immune responses against both viruses, although further studies will be needed to test whether it protects against disease.
- Study participants will continue to be monitored for more than a year to assess the vaccine’s safety and how durable these immune responses are.
An experimental vaccine designed to protect against both Lassa fever and rabies has shown promising results in its first human trial.
The findings raise hopes for a new tool against two deadly viral diseases that disproportionately affect parts of West Africa.
Lassa fever and rabies pose different public health challenges. While effective rabies vaccines exist, there are currently no licensed vaccines against Lassa fever.
Because both diseases affect many of the same regions of West Africa, researchers have been investigating whether a single vaccine could help protect against both.
“By combining targets into a single product, it could reduce the need for separate vaccination efforts, and streamline delivery in settings where access is limited,” said Prof Justin Ortiz at the University of Maryland in Baltimore, US, who led the research.
Why develop a dual vaccine against rabies and Lassa virus?
Lassa fever is a viral haemorrhagic disease that circulates in several West African countries, including Nigeria, Sierra Leone, Liberia and Guinea.
Spread mainly by rodents, the virus causes an estimated 100,000 to 300,000 infections and approximately 5,000 deaths each year, although the true burden is thought to be considerably higher because many cases go undiagnosed or unreported.
While many infections are mild or asymptomatic, severe cases can lead to bleeding, organ failure and death.
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The disease is also particularly dangerous during pregnancy, with more than 80% of late-term infections resulting in the death of the mother or foetus.
Although there are currently no licensed vaccines against Lassa virus, several candidates are currently being tested in humans. The most advanced is a single-dose vaccine developed by IAVI, which is currently in Phase 2 trials in West Africa.
Rabies presents a different challenge. Here, human vaccines already exist that can prevent disease both before and after exposure.
Yet rabies still causes an estimated 59,000 deaths globally each year because many people are unable to access vaccines, post-exposure treatment and healthcare services quickly enough after being bitten by a potentially rabid animal.
Because rabies and Lassa fever overlap geographically in parts of West Africa, researchers have been exploring whether a single vaccine could help protect against both diseases. If successful, this approach could potentially simplify vaccine delivery and reduce costs in regions where healthcare resources are often stretched.
How does the dual Lassa and rabies vaccine work?
The experimental vaccine, known as LASSARAB, is based on an inactivated rabies virus that has been genetically engineered to carry a key protein from the Lassa virus.
This trains the immune system to recognise and respond to both viruses, potentially providing protection against rabies as well as Lassa fever.
The vaccine can also be freeze-dried for storage, which could make distribution easier in settings where maintaining a cold chain is difficult.
To test the vaccine, the researchers enrolled 54 healthy adults in the US and randomly assigned them to receive one of three doses of LASSARAB or a licensed rabies vaccine as a control.
Participants received two injections 28 days apart and were monitored for side-effects and immune responses.
Can the vaccine protect against Lassa fever and rabies?
While it is still too early to know whether this vaccine candidate prevents disease, all participants who received it developed antibodies against the Lassa virus protein targeted by the vaccine, while antibody responses against rabies reached levels considered protective. No serious vaccine-related adverse events were reported. The research was published in Nature Medicine.
“These findings support continued development of this vaccine and underscore the potential of the rabies-vector platform to address the urgent need for countermeasures against two priority pathogens,” the researchers said.
Participants will continue to be followed for more than a year to assess the vaccine’s safety, how durable these immune responses are and whether the vaccine should advance to larger clinical trials.
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