Scientists have developed a new vaccine candidate against COVID-19 based on the yellow fever vaccine, a single dose of which protects hamsters and monkeys from infection with the SARS-CoV-2 coronavirus.
The researchers at the Rega Institute at KU Leuven in Belgium are currently preparing for clinical trials of the vaccine candidate.
To develop the vaccine, tentatively named RegaVax, the researchers inserted the genetic code of the SARS-CoV-2 virus spikes into that of the yellow fever vaccine.
RegaVax is a vector vaccine which uses the genetic code of the yellow fever vaccine virus as a carrier for the genetic code of the coronavirus spikes.
According to an early version of the research paper accepted for publication in the journal Nature, the researchers tested the vaccine in healthy hamsters and monkeys, with another group of the animals receiving a placebo.
The researchers first vaccinated the hamsters and then dripped the virus into their noses.
They found that ten days after a single vaccine dose, most of the hamsters were protected against the virus, adding that three weeks after vaccination, all hamsters were protected.
“They also didn’t develop any lung infections. The lungs of the hamsters in the control groups, by contrast, showed clear signs of infection and disease,” explained Professor Johan Neyts from KU Leuven.
The team also tested the vaccine in monkeys.
“In some of the monkeys, we observed neutralising antibodies already seven days after vaccination. After fourteen days, high titers of neutralising antibodies were measured in all animals,” Neyts said.
“This is very fast. Moreover, in the vaccinated animals, the virus was completely or nearly completely gone from their throats,” he said.
“Ours is the only vaccine currently in development against COVID-19 that also protects against yellow fever,” explained Neyts.
Previously, the Rega team said they have used the yellow fever vaccine as the foundation for vaccine candidates against Zika, Ebola, and rabies.
“The effectiveness and safety of the yellow fever vaccine, which has been in use for 80 years, is well-established. More than 500 million people have already received this vaccine. One dose offers fast protection against yellow fever that in nearly all cases lasts for life,” Neyts said.
“A vaccine that works against COVID-19 and yellow fever could offer an important contribution to the WHO’s campaign to eradicate yellow fever by 2026,” Neyts noted.
“Especially now that we know there are mosquito species present in Asia that can transmit the yellow fever virus,” he said.
The researchers said RegaVax works after one dose, unlike many of the front-runners in the race today, which require a repeat vaccination after one month. “This has important logistical implications, in particular for countries with a less advanced medical system,” explained Neyts.
“Additionally, we expect that the vaccine will offer long-lasting immunity to COVID-19. 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 said.
The vaccine can be stored at 2-8 degrees Celsius, while some vaccines require a cold chain with temperatures down to minus 70 degrees Celsius, the researchers said.
“That’s already challenging in the Western world, but it may be nearly impossible to vaccinate large populations in remote tropical and subtropical regions,” Neyts added.