Coronavirus vaccine: AstraZeneca and Oxford University encouraged by trial results showing immune response
The Covid-19 vaccine being developed by AstraZeneca and Oxford University generated a strong immune response in clinical trials, it has been confirmed.
The vaccine also appears safe, generating no serious adverse reactions in patients.
Dr Mene Panagalos, from the Cambridge-based pharmaceutical company, said although there was more testing to be done, the results were encouraging and increased “confidence that the vaccine will work”.
AstraZeneca is proceeding with plans to manufacture the vaccine at scale, including 100 million doses for the UK.
Some 1,077 healthy adult volunteers, aged 18-55, are involved in the ongoing phase I/II trial of the vaccine candidate - named AZD1222 - which is being led by Oxford University.
The blinded, multi-centre randomised controlled trial assessed a single dose against a meningococcal conjugate vaccine, called MenACWY, for comparison.
Ten participants also received two doses of AZD1222 one month apart.
The primary purpose of the trials was to show the vaccine was safe, and provoked an immune response.
Interim results, published in The Lancet today (Monday) show a single dose led to a fourfold increase in antibodies to the SARS-CoV-2 virus spike protein in 95 per cent of participants one month after injection. Antibodies are proteins produced by the immune system to neutralise pathogens.
In all participants, a T-cell response was also induced, peaking by day 14, and maintained two months after injection. T cells are a type of white blood cell that form a key part of the immune system, controlling the body’s response to infection and helping to destroy invaders.
Effective vaccines typically provoke both an antibody and T cell response, and it is thought a “rapid induction” of both against the virus could provide important protection.
Emerging data suggests that a T-cell response could play a key role in helping beat the disease. In some individuals who have been infected with the virus but remained asymptomatic, no antibodies have been detectable, but a robust T-cell response has been seen.
In this trial, neutralising activity against the SARS-CoV-2 virus was seen in 91 per cent of participants one month after vaccination and in 100 per cent of participants who received a second dose.
The results show the levels of neutralising antibodies seen in participants receiving either one or two doses were similar to those seen in convalescent Covid-19 patients.
Dr Mene Pangalos, executive vice president, biopharmaceuticals R&D, said: “We are encouraged by the Phase I/II interim data showing AZD1222 was capable of generating a rapid antibody and T-cell response against SARS-CoV-2. While there is more work to be done, today’s data increases our confidence that the vaccine will work and allows us to continue our plans to manufacture the vaccine at scale for broad and equitable access around the world.”
It is made from a weakened version of a common cold virus, known as an adenovirus, that causes infections in chimpanzees. It has been genetically changed so that it is impossible for it to replicate in humans.
The vaccination prompts the production of the surface spike protein, which primes the immune system to attack the SARS-CoV-2 virus if it later infects the body.
Volunteers in the test group experienced similar reactions to those seen in previous trials and with other adenoviral vector vaccines, included temporary pain and tenderness at the site of the injection, mild-to-moderate headaches, fatigue, chills, feverishness, malaise and muscle ache, but no serious reactions.
Paracetamol helped to lessen these side effects, which occurred less frequently after a second dose.
Professor Andrew Pollard, chief investigator of the Oxford Vaccine Trial at Oxford University and co-author of the trial, said: “The interim phase I/II data for our coronavirus vaccine shows that the vaccine did not lead to any unexpected reactions and had a similar safety profile to previous vaccines of this type.
“The immune responses observed following vaccination are in line with what we expect will be associated with protection against the SARS-CoV-2 virus, although we must continue with our rigorous clinical trial programme to confirm this. We saw the strongest immune response in participants who received two doses of the vaccine, indicating that this might be a good strategy for vaccination.”
Testing is ongoing, with late-stage phase II/III trials under way in the UK, where more than 10,000 people will take part, along with 2,000 in South Africa. It is about to be extended to 5,000 people in Brazil and 30,000 people n the US.
Running the trials in countries where the coronavirus infection is still rife, such as Brazil and the US, is key to prove its effectiveness.
These trials will determine how well the vaccine will protect against Covid-19 as well as measuring the safety and immune responses in different age ranges and at various doses.
AstraZeneca has committed to ensuring “broad and equitable access” to the vaccine, if these late-stage clinical trials are successful.
Depending on this, the first doses could be available this year, with health and care workers prioritised, along with those at high risk from Covid-19, although widespread availability is more likely next year.
It has already agreed to supply more than two billion doses of the vaccine with the UK, US, Europe’s Inclusive Vaccines Alliance, the Coalition for Epidemic Preparedness, Gavi the Vaccine Alliance and Serum Institute of India.
Meanwhile, the UK has also confirmed it has agreed to purchase 30 million doses of an alternative vaccine under development by BioNTech and Pfizer, and 60 million doses of another being created by Valneva.
It has agreed in principle to buy one million doses of a treatment containing Covid-19 neutralising antibodies being created by AstraZeneca. This is designed to protect those who cannot receive vaccines such as cancer and immunocompromised patients.
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More by this authorPaul Brackley
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