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Oxford Covid-19 Vaccine Trial Invokes Immune Responses

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(Ewa Urban, Pixabay)

20 July 2020. Results from a clinical trial testing a Covid-19 vaccine show the vaccine invokes two types of immune responses without serious adverse effects. The vaccine is being developed by the Jenner Institute and Oxford Vaccine Group at University of Oxford in the U.K., with results of the trial reported today in the journal The Lancet.

The Oxford vaccine code-named ChAdOx1 nCoV-19 is based on the ChAdOx1 vaccine framework, derived from an adenovirus in chimpanzees, similar to a virus in humans considered benign, or responsible at most for symptoms like the common cold. In this case, the adenovirus is genetically engineered to keep from replicating in humans, with genetic material added to make proteins similar to the characteristic spike glycoprotein on the surface of SARS-CoV-2 viruses. That spike protein binds to receptors in human cells, to gain entry and cause Covid-19 infections.

ChAdOx1 nCoV-19 is designed to generate an immune response to the spike protein that stops the protein from binding to receptors on human cells, thus preventing infections. The university says other vaccines made from the ChAdOx1 framework were tested so far in some 320 individuals, and found generally safe and well-tolerated, with adverse side effects reported including fever, headache, and soreness in the arm receiving the vaccine.

The early- and mid-stage clinical trial is enrolling some 1,100 healthy adults in England, age 18 to 55, randomly assigned to receive either ChAdOx1 nCoV-19 or the standard MenACWY vaccine approved to prevent against meningococcal infections that can lead to meningitis. The MenACWY vaccine is given for comparison instead of the usual saline solution to better gauge reactions to the Covid-19 vaccine, instead of adverse reactions to vaccines in general. Part of the sample is also receiving paracetamol, an over-the-counter pain killer, taken before vaccine injections to prevent adverse effects.

Most of the 1,077 participants received either a single dose of the Covid-19 or MenACWY vaccine, but 10 members of each group also received a second booster dose four weeks after the first injection. The results show after 14 days, Covid-19 vaccine recipients increased their volume of spike-specific T-cells by a median of 856 per million blood cells. These T-cells bind on and attack the invading viruses. And after 28 days, Covid-19 vaccine recipients also produced neutralizing immunoglobulin G, or IgG antibodies, in 91 percent of single-dose recipients and all of the double-dose — first and booster injection — recipients.

Results show as well that recipients generally tolerated the Covid-19 vaccine, with no serious adverse effects. However, many vaccine recipients reported mild and transient reactions including chills, fever, headache, and muscle pain. Participants given paracetamol before the injections, experienced fewer of those reactions.

Infectious disease professor Andrew Pollard who led the trial, says in an Oxford Vaccine Group statement that the “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,” adding that the “immune responses observed following vaccination are in line with what previous animal studies have shown are associated with protection against the SARS-CoV-2 virus.”

As reported in Science & Enterprise in April, drug maker AstraZeneca agreed to help develop, manufacture, and distribute the ChAdOx1 nCoV-19 vaccine. The agreement calls for AstraZeneca to work with the Oxford spin-off company Vaccitech to get the vaccine in the hands of medical authorities in the U.K. as soon as possible, and internationally, including low- and middle-income regions.

Oxford and AstraZeneca say the next steps are late-stage trials with large samples to confirm these results. Clinical trials with 30,000 participants are planned in the U.S., with similar studies already underway in Brazil and South Africa, as well as a separate trial with children.

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