This story originally appeared on WIRED UK.“When the world got the virus [RNA] sequence through on January 11, we knew pretty well immediately what kind of vaccine one would need and what bit of virus you would need to put in it, so the world of immunology was in a very good state to get going on that,” says Danny Altmann, a professor of immunology at Imperial College London.
On July 20, two vaccine candidates published preliminary results from Phase I and II trials showing they induced an immune response and didn’t trigger any major safety concerns, marking a positive step forward. But there’s still a way to go. Inducing an immune response doesn’t necessarily mean that the vaccine will actually protect people from Covid-19. Only a Phase III trial, which involves giving a large number of people the vaccine and tracking if they get the disease, will show this. “They’ve done everything we wanted, so that’s good news,” Altmann says. “Now it’s the difficult bit.”The vaccine candidates currently in development make use of a range of different vaccine technology platforms, some of which are tried-and-tested and others that are really cutting-edge. While some first results have started to come out, it’s not possible to draw direct comparisons, as different labs can test with different doses and populations, and use different assays to measure the immune response. “The question of which one is better cannot be answered at this point,” says Beate Kampmann, director of the Vaccine Centre at the London School of Hygiene and Tropical Medicine.
With that in mind, here are some of the vaccine candidates that are currently furthest along:Oxford/AstraZenecaThe world has heard a lot about a vaccine being developed at the University of Oxford in partnership with the pharmaceutical firm AstraZeneca. The UK government has already ordered 100 million doses of the vaccine, and it is currently one of the front-runners in terms of testing.The Oxford vaccine is a viral vector vaccine: It is based on a chimp adenovirus (a virus that causes an illness like the common cold in chimpanzees), which has been modified to contain a genetic sequence of the coronavirus “spike protein,” which is thought to play a large role in infecting cells. This is a way of exposing the body to the spike protein without exposing it to coronavirus, so that it creates an immune response. “The chimp adenovirus is kind of the Trojan horse to bring the Covid protein information into the immune system,” Kampmann explains. If the immune system then comes into contact with the actual coronavirus, it’s primed to react.
On July 20, researchers published a preliminary report in The Lancet on Phase I and II studies of their vaccine, ChAdOx1 nCoV-19, which they report induced an immune response and didn’t have any major side effects. It is now moving into Phase III trials in Brazil and South Africa.Altmann says the immune response shown in the Oxford data is promising and emphasizes the importance of triggering T cells as well as antibodies. T cells are a type of white blood cell that help B cells create antibodies and kill infected cells to help stop an infection from spreading. “For any good response from a vaccine, you need both on board,” Altmann says. He says that all the data he has seen from vaccine candidates looks good for both—“although I thought the Oxford data had really truly impressive T cell data.”
CanSinoChina’s CanSino Biologics reported results from its Phase II trial, which was conducted in Wuhan, on the same day as the Oxford group, also in The Lancet. It similarly reported that its vaccine was safe and induced a significant immune response.