Here’s hoping: scientists may have got Covid-19 vaccine down to a T
Researchers say trials currently running in SA and Brazil stand a very good chance of providing a cure
Scientists at Oxford in the UK believe they have made a breakthrough in their quest for a Covid-19 vaccine after discovering that the jab triggers a response that may offer a “double defence” against the virus.
Phase 1 human trials of the world-leading Oxford vaccine have shown that it generates an immune response against the disease.
Blood samples taken from a group of UK volunteers given a dose of the vaccine showed that it stimulated the body to produce antibodies and “killer T-cells”, a senior source said.
The discovery is promising because separate studies have suggested that antibodies may fade away within months, while T-cells can stay in circulation for years.
However, the source cautioned that the results, while “extremely promising”, did not yet prove that the Oxford vaccine provided long-lasting immunity against Covid-19.
“I can tell you that we now know the Oxford vaccine covers both bases — it produces both a T-cell and an antibody response,” the source said. “It’s the combination of these two that will hopefully keep people safe. It’s an important moment, but we still have a long way to go.”
Another source close to the team described the presence of antibodies and T-cells as a potential “double defence” against Covid-19. The full findings will be published in The Lancet medical journal on Monday.
The findings are based on initial results from the Phase 1 clinical trial, which began in April, when doses of the vaccine were given to 500 volunteers. A trial involving 5,000 volunteers in Brazil to prove the vaccine is effective is also under way, while UK drugmaker AstraZeneca has signed a deal to produce up to two billion doses. If all goes well, the researchers, led by Prof Sarah Gilbert, hope the vaccine may be ready as early as October.
The initial data also suggest that the ChAdOx1 nCoV-19 vaccine is safe, with no major side effects, it is understood, though further work will be needed. The team is also evaluating the level of dose needed to produce an effective response.
David Carpenter, chair of the Berkshire Research Ethics Committee which approved the Oxford trial and continues to work with scientists on amendments, said the team was “absolutely on track”.
“They can strengthen findings by targeting people in hospitals, health-care professionals, where the spread is [more] likely to happen. Nobody can put final dates ... things might go wrong, but the reality is that by working with a big pharma company, that vaccine could be fairly widely available about September and that is the sort of target they are working on.”
The T-cell discovery is likely to be important because scientists increasingly believe that any successful vaccine will need to trigger the production of antibodies and T-cells, which directly attack human cells that have already become infected with viruses.
Earlier this year, a similar vaccine against MERS, invented by the same Oxford team, was found to elicit high levels of T-cells, but only triggered neutralising antibodies in 44% of volunteers.
If the Covid vaccine can be proven in further trials to elicit a similarly strong T-cell response, the team hopes it may not need to trigger high levels of antibodies to provide meaningful protection. A number of other vaccine candidates across the world have also produced T-cell responses, but only in smaller-scale studies. Others including a major project in China are thought to be unlikely to produce T-cells when tested on humans.
This week, US biotech company Moderna published data from a Phase 1 trial involving 45 people showing that its RNA vaccine triggered neutralising antibodies and T-cells. The findings come amid increasing gloom over the longevity of Covid-19 antibodies.
Earlier this week, a King’s College London study found people who recovered from Covid-19 appeared to lose their antibodies within months.
But in a study published in Nature, researchers found T-cells from the SARS outbreak had lasted for 17 years. Duke University scientists in Singapore found T-cells were still circulating in potent quantities from patients who were infected in 2003. It is not known for sure if the same will be true for Covid-19, and whether the T-cells will protect against reinfection, but the lead researcher described discovery as “potentially very significant for a vaccine”.
The researchers also found “remarkable” levels of T-cells able to latch on to the Covid-19 virus within people who had never been infected with the disease. They believe these may have been triggered by the common cold and other animal coronaviruses, mainly originating in bats, and that the primed cells may also offer protection against the new virus.
Prof Antonio Bertoletti, who led the research in Singapore, said this may explain why so few patients in Singapore and South East Asia have had severe infections. He said while these T-cells will be more common in Asia, they will be present about the world. It suggests a significant proportion of all populations will have a degree of natural immunity to Covid-19.
Clinical trials of the Oxford vaccine, involving more than 8,000 participants, are almost complete. The focus has now moved to Brazil and SA, and scientists hope to gather sufficient cases within about a month.
What the latest research means for our defence against the virus
Q Does it work?
A The clinical trials have, so far, been successful. Researchers have shown that antibodies produced against sections of a genetic material, called “spike proteins” and usually found on the surface of the coronavirus after infection, are able to kill the virus when tested in the laboratory. They want the human body to recognise and develop antibodies to the protein that would stop the virus from entering human cells. Trials suggest that not only is this happening, but also that the body is developing a crucial T-cell response, which is deemed vital in the defence against Covid-19.
Q When will it be available?
A AstraZeneca is on track to begin rolling out up to two billion doses of a coronavirus vaccine in September, if ongoing trials continue to prove successful. It has already started to manufacture the vaccine. Britain would reportedly be the first to get the vaccine and an extra £84m (about R1,7bn) in funding to accelerate research was announced.
Q What is the next step?
A As the level of coronavirus in the UK subsided, scientists began testing the drug in hospitals. They have also enrolled 5,000 volunteers in Brazil and others in SA. The developers are expected to report their Phase I study results, which would show whether it is safe and whether it induces an immune response, within the next fortnight.
A combined response may be the trigger to fight the virus
Scientists increasingly believe that any successful vaccine may need to trigger an antibody and T-cell response, the two key aspects of our “adaptive” immune system.
Antibodies, produced by B-cells, recognise a virus circulating in our body and neutralise it, preventing it from entering our cells.
T-cells are slightly different. They help to make antibodies, but also directly attack human cells that have become infected. These cells are vital in fighting several illnesses, including measles and the common cold.
When we have fought off an infection once, we retain a number of “memory” cells that are primed and ready to attack if we are infected with the virus again. It is this process that a vaccine is attempting to replicate.
“The best vaccines tend to be those that mimic a viral infection and this ‘natural’ infection would trigger both antibodies and T-cells,” said Prof Jonathan Ball, a virologist at the UK’s University of Nottingham.
— Telegraph Media Group Limited (2020)