Virologists at KU Leuven’s Rega Institute have developed a candidate vaccine against Covid-19. One of the first Covid vaccine candidates in the world that has proven to protect lab animals from infection, the team aims to start clinical trials by the end of the year.

The research team, led by virologists Johan Neyts and Kai Dallmeier, started developing vaccine prototypes six months ago. One has now proven to be highly effective in warding off the virus in hamsters. The animals that received the vaccine had few to no traces of the virus in their lungs after exposure.

To study the efficacy of the vaccine candidates, the virologists first developed a hamster model. When hamsters receive the Sars-CoV-2 virus through their nose, they develop a lung infection 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 fewer virus particles than in the control groups,” says professor Neyts. “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.”

A single dose of the vaccine candidate proved sufficient to prevent infection. Moreover, many animals were already protected within 10 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 used the same approach to develop vaccine candidates against Ebola, Zika and rabies.

“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,” says Neyts.

Now the lab is negotiating with potential vaccine producers in order to test the vaccine on people. “If everything keeps going according to plan, we want to start the first clinical trials with human subjects by the end of this year,” says Dr Dallmeier, who leads the vaccine development team at KU Leuven.

It generally takes at least 10 years to develop a vaccine, but the seriousness of Covid-19 led the lab to concentrate solely on developing candidates. “And we’re not alone,” says Dallmeier. “Worldwide, many vaccines are in development. That is a good thing because, in this stage. It’s important not to put all our eggs in one basket.”

Neyts notes that the institute is also looking for a cure for Covid-19. “Vaccines only offer protection when people are vaccinated well before they are exposed to the virus,” he explains. “Vaccines are not a solution for people who are already ill. That is why we are also looking for a cure to help Covid-19 patients.”

Right about the time that Belgium went into lockdown, the Rega Institute hit the headlines with the news that 15,000 medicinal compounds were being flown over from the USA for rapid testing against the coronavirus. Being chosen for this task by the Bill & Melinda Gates Foundation was a high-profile endorsement of the Institute’s preparations for the challenge of a virus pandemic.

“We’re currently analysing thousands of compounds of existing medicines to find out whether some may already be useful to slow down the virus in Covid-19 patients,” confirms Neyts. The most promising of these drugs and combinations of drugs are also being tested in hamsters. “We hope to be able to suggest combinations for studies with patients.