Today, virologists at the KU Leuven Rega Institute published the results of their pre-clinical study into a Covid-19 vaccine candidate in Nature. Their paper builds on a preprint that the team shared on bioRxiv earlier this year, and that we reported on. The vaccine candidate is based on the yellow fever vaccine and thus also protects against yellow fever.
In the preprint, the authors shared the results of their tests of the vaccine candidate in hamsters. "In the hamsters that received the vaccine candidate, we found up to half a million times fewer 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," Professor Johan Neyts explained at the time.
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In the final paper, his team also added data of tests 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. This is very fast. Moreover, in the vaccinated animals, the virus was completely or nearly completely gone from their throats."
The team now expects to start clinical trials in the second quarter of 2021. They have joined forces with a specialised and accredited company that will produce the vaccine candidate for testing in humans.
Diversification of the Covid-19 vaccine landscape
While the final vaccine will likely not be available until 2022, Professor Neyts sees some important benefits. "A vaccine that works against Covid-19 and yellow fever could offer an important contribution to the WHO campaign to eradicate yellow fever by 2026 ," Neyts continues. "Especially now that we know about the presence of mosquito species in Asia that can transmit the yellow fever virus."
The vaccine candidate 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," explains Professor 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."
A vaccine that works against Covid-19 and yellow fever could offer an important contribution to the WHO campaign to eradicate yellow fever by 2026.
- virologist Johan Neyts
Finally, the vaccine candidate can be stored at 2-8 °C, while some vaccines require a cold chain with temperatures down to -70 °C. "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 explains.
"An inexpensive, single-dose vaccine that rapidly protects against infection, that can be stored and transported at fridge temperature, and that may, like the yellow fever vaccine on which it is based, result in long-lasting immunity, provides an important and much-needed diversification of the Covid-19 vaccine landscape," Neyts concludes.