Virus Vaccine Update
A little long but informative.
From The Telegraph:
Oxford scientists 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 I human trials of the world-leading Oxford vaccine have shown that it generates an immune response against the disease, the Telegraph has learned.
Blood samples taken from a group of UK volunteers given a dose of the vaccine showed that it stimulated the body to produce both 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 provides 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 senior source told the Telegraph.
“It’s the combination of these two that will hopefully keep people safe.
“So far, so good. It’s an important moment. But we still have a long way to go.”
Another source close to the team described the presence of both antibodies and T-cells as a “double defence” against Covid-19.
The full findings will be published in the Lancet medical journal on July 20, it was confirmed on Wednesday night.
The findings are based on initial results from a Phase 1 clinical trial, which began in Oxford in April when doses of the vaccine were given to 500 volunteers. A major trial is currently underway involving 5,000 volunteers in virus-hit Brazil to prove the vaccine is effective, while the drugmaker AstraZeneca has signed a deal to produce up to two billion doses. If all goes well, the researchers hope the vaccine may be ready as early as October.
Speaking on Peston on ITV on Wednesday night, Matt Hancock, the Health Secretary, said the best case scenario is for the vaccine to be available this year, but added it will "more likely" be ready in 2021.
The initial data also suggests that the ChAdOx1 nCoV-19 vaccine is safe with no major side effects, it is understood, although further work will be needed. The team is also evaluating the level of dose needed to produce an effective response.
Stocks soared on Wednesday after reports of positive news on the Oxford vaccine to be released next week. Shares in AstraZeneca, the drugmaker licensed to produce billions of doses of the Oxford vaccine, jumped 5.2 per cemt.
David Carpenter, chair of the Berkshire Research Ethics Committee (REC), which approved the Oxford trial and continues to work with scientists on amendments, told the Telegraph that the team were “absolutely on track”.
“They can strengthen findings by targeting people in hospitals, healthcare 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 around 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 both 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 per cent 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 the US biotech company, Moderna, published data from a phase one trial involving 45 people showing that its RNA vaccine triggered both neutralising antibodies and T cells.
The findings come amid increasing gloom over the longevity of Covid-19 antibodies. Earlier this week, a Kings College study found that people who recovered from Covid-19 appeared to lose their antibodies within months.
But in a study published in Nature today researchers found that 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 re-infection, but, speaking to The Telegraph, 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 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.
Professor Bartoletti, who led the research in Singapore, said this may explain why so few patients in Singapore and South East Asia have had really severe infections.
He said that while these T Cells will be more common in Asia, they will be present around 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, marking phase III in the UK and involving more than 8,000 participants, are now almost complete. The focus has now moved to Brazil and South Africa, where the disease is more prevalent, and scientists hope to gather sufficient cases within around a month.
Antibodies vs T-cells
Scientists increasingly believe that any successful vaccine may need to trigger both 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 already become infected with a virus. These cells are vital in fighting a number of 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 – and it is this process that a vaccine is attempting to replicate.
"What I would say is that if a vaccine elicits both responses it is potentially going to be better than one that just elicits one arm of the immune system," said Professor Jonathan Ball, a virologist at the University of Nottingham.
"The best vaccines tend to be those that mimic a viral infection, and this 'natural' infection would trigger both antibodies and T-cells."
Research published in the last few weeks appears to underline the importance of triggering a broad immune response.
A team at King's College London has found that antibodies do not remain in our blood for long. Of 96 people tracked, 60 per cent had a "potent" Covid-19 antibody response at the height of their infection.
This fell to just 17 per cent three months later – in some, antibodies were almost undetectable.
Separately, studies have detected T-cell reactivity against Sars-CoV-2 in those who have never been exposed to the virus.
But Professor Beate Kampmann, director of the Vaccine Centre at the London School of Hygiene and Tropical Medicine, warned that this does not mean vaccines which fail to produce T-cells will not be effective.
Fading antibodies do not necessarily equate to fading immunity – it is entirely possible that antibodies in our blood may fall below detectable levels while still providing an effective defence against reinfection.
Likewise, just because a candidate elicits a T-cell response, this "does not guarantee that it will be safe and effective".
"A safe and effective vaccine is not just around the corner, and there are many unknowns – much bigger datasets and trials are needed," warned Prof Kampmann.
10 vaccine candidates are in human trials
Stage of clinical trial Lead partner Country
Phase 2 Cansino China
Phase 1/2 Beijing Institute of Biotechnology China
Phase 1/2 Sinovac Biotech China
Phase 1/2 Wuhan Institute of Biological Products China
Phase 1/2 AstraZeneca / Oxford UK
Phase 1/2 Shenzhen Geno-Immune Medical Institute China
Phase 1/2 Pfizer/ BioNTech Germany
Phase 1 Shenzhen Geno-Immune Medical Institute China
Phase 1 Inovio Pharmaceuticals USA
Phasee 1 Moderna Pharmaceuticals USA
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