First potential Lassa fever vaccine set for trial by year’s end

Scientists are rushing to find a vaccine for Lassa fever, and their efforts may have borne fruit in the form of a measles-platform based concoction that they now intend to put through human clinical trials by the end of the year.

Lassa, which infects up to 300,000 people per year and kills between 5,000 and 6,000, is a hemorrhagic fever endemic to West Africa. The World Health Organization (WHO) has listed it as an epidemic threat requiring urgent research and development. This year, scientists at the Biology of Viral Emerging Infections Unit and the Viral Genomics and Vaccination Unit at the Institut Pasteur evaluated several vaccines for the rodent-carried disease.

“The most effective vaccine, the one based on the measles vaccine platform expressing LASV antigens, was recently selected by the CEPI (Coalition for Epidemic Preparedness Innovations) to enter clinical trials in humans by the end of the year,” Sylvain Baize, Head of the Biology of Viral Emerging Infections Unit and last author of the study, said.

In their analyses, scientists sought a vaccine that could offer protection with a single injection, to make it most effective during an outbreak. They used vaccine platforms based on live viruses that used a recombinant Mopeia virus hyperattenuated by the scientists, as well as a recombinant measles vaccine strain created by Frédéric Tangy, Head of the Institut Pasteur’s Viral Genomics and Vaccination Unit.

“We compared the efficacy of these vaccines in preventing LASV infection in a preclinical animal model. The vaccines were well tolerated and induced protection against Lassa fever after a single shot, but with different levels of efficacy,” Mathieu Matéo, a scientist in the Institut Pasteur’s Biology of Viral Emerging Infections Unit and lead author of the study, said.

In the selected vaccine, protection began two days after immunization. The results of this research were published in Science Translational Medicine earlier this month.