The research suggests that the newly developed vaccine would not only protect against COVID-19 but also against yellow fever.
In addition, it appears to provide protection after a single shot, whereas SARS-CoV-2 vaccines such as the one that Pfizer and BioNTech have developed require two doses 1 month apart.
“This has important logistical implications, in particular for countries with a less advanced medical system,” explains Prof. Johan Neyts, from the Rega Institute at KU Leuven in Belgium. Prof. Neyts is one of the virologists who led the research.
“It could therefore be an ideal candidate for repeat vaccinations when immunity decreases in people who have received one of the first-generation vaccines,” he says.
The study, which appears in the journal Nature and as a preprint, suggests that a single shot of the vaccine protected hamsters against SARS-CoV-2, which is the virus that causes COVID-19. It also protected mice and monkeys.
The team is now preparing to conduct clinical trials of the new vaccine, which is provisionally called RegaVax, in 2021.
The standard yellow fever vaccine, known as YF17D, has been in use for 80 years and has a good safety record. It delivers a live, “attenuated” (weakened) strain of the yellow fever virus.
The team at KU Leuven had previously used the same virus as the basis of candidate vaccines against the Zika, Ebola, and rabies viruses.
The scientists use the yellow fever virus as a “vector” to deliver fragments of genetic material from other viruses. The fragments provoke a targeted immune response and long-term immunity to future infections.
Vaccines that employ the yellow fever virus as a vector are already licensed for use against Japanese encephalitis and dengue viruses.
The sequence is a blueprint for SARS-CoV-2 spike proteins, which give the virus its characteristic crown-like appearance. When host cells become infected with the weakened yellow fever virus, they make copies of the spike, which, in turn, provoke an immune response.