To study the efficacy of the vaccine candidates in-depth, the virologists first developed a hamster model. When hamsters receive the SARS-CoV-2 virus through their nose, they develop a lung infection that is similar to COVID-19.
Healthy hamsters were first vaccinated and exposed to the virus a couple of weeks later. Control groups each received one of two alternatives: the yellow fever vaccine, or a placebo.
"In the hamsters that received the vaccine candidate, we found up to half a million times less virus particles than in the control groups. These animals also didn't develop any lung infections. The lungs of their counterparts in the control groups, by contrast, showed clear signs of infection and disease," Neyts explains. A single dose of the vaccine candidate proved sufficient to prevent infection. Moreover, several animals were already protected within ten days after vaccination.
The vaccine candidate is based on the existing vaccine against yellow fever and may thus protect lab animals against both COVID-19 and yellow fever. The researchers inserted parts of the genetic code of the SARS-CoV-2 virus into the yellow fever vaccine. In the past, the KU Leuven team already used the same approach to develop vaccine candidates against Ebola, Zika, and rabies.
"The effectiveness of the yellow fever vaccine is well-established," Neyts continues. "The vaccine has been in use for about eighty years, and close to 800 million people have already received it. One dose of the vaccine offers lifelong protection against yellow fever. More than 160 vaccines against COVID-19 are currently in development, but ours is the only one that is based on the yellow fever vaccine."
End quote
The Yellow Fever vaccine also gives partial protection against West Nile Fever virus
