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Trials of a coronavirus vaccine being developed by AstraZeneca and the University of Oxford will resume after a hiatus due to a reported side effect in a patient in the UK.
AstraZeneca issued a statement Tuesday night saying that studies on the latest stage of the vaccine had been halted while the company investigated whether the patient-reported side effect is related to the vaccine.
On Saturday, Oxford University confirmed that trials would resume at all UK clinical trial sites.
Health Secretary Matt Hancock welcomed the reboot, saying: “Good news everyone – the Oxford vaccine trials are back on track. This pause shows that we will always prioritize safety. We will support our scientists to provide an effective vaccine as soon as safely possible. “
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It comes after the government’s top scientific adviser, Sir Patrick Vallance, told a Downing Street press conference that what happened at the Oxford trial is not unusual. He added that similar events should also be expected in some of the other vaccine candidate trials.
News site Stat first reported the pause in testing, saying the possible side effect occurred in a test volunteer in Britain, who was expected to recover.
The vaccine is being tested in thousands of people in Britain and the United States, and in smaller study groups in Brazil and South America.
Oxford University said: “Ongoing randomized controlled clinical trials of the Oxford ChAdOx1 nCoV-19 coronavirus vaccine will resume at all UK clinical trial sites.
“Worldwide, about 18,000 people have received the study vaccines as part of the trial. In large trials like this one, some participants are expected to feel unwell and each case must be carefully evaluated to ensure a careful assessment of safety.
“On Sunday, September 6, our standard review process caused a pause in the vaccination study in all of our global trials to allow for review of safety data by an independent safety review committee and national regulators. All routine follow-up appointments continued normally during this period.
“The independent review process has been completed and, following the recommendations of the independent safety review committee and the UK regulator, the MHRA, trials will resume in the UK.”
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No details were provided about the patient or the nature of the side effect, but New York Times has previously reported that the patient had been diagnosed with transverse myelitis, an inflammatory syndrome that affects the spinal cord and is often caused by viral infections.
Temporary withholdings of large medical studies are not uncommon, and the investigation of unexpected reactions is a mandatory part of safety testing.
Two other vaccines are in huge end-stage trials in the United States, one made by Moderna and the other by Pfizer and Germany’s BioNTech. However, the University of Oxford has said that a vaccine may not be ready before 2022.
How do scientists develop vaccines for new viruses?
Vaccines work by tricking our bodies into believing that we have been infected by a virus. Our body generates an immune response and creates a memory of this virus that will allow us to fight it in the future.
Viruses and the immune system interact in complex ways, so there are many different approaches to developing an effective vaccine. The two most common types are inactivated vaccines (which use harmless viruses that have been ‘killed’ but still activate the immune system) and attenuated vaccines (which use live viruses that have been modified to trigger an immune response without causing us to damage).
A more recent development is recombinant vaccines, which involve genetically engineering a less harmful virus to include a small part of the target virus. Our body launches an immune response to the carrier virus, but also to the target virus.
In recent years, this approach has been used to develop a vaccine (called rVSV-ZEBOV) against the Ebola virus. It consists of an animal virus from vesicular stomatitis (which causes flu-like symptoms in humans), designed to have an external protein from the Zaire strain of Ebola.
Vaccines go through a great deal of testing to verify that they are safe and effective, if there are any side effects, and what dose levels are appropriate. It usually takes years before a vaccine is commercially available.
Sometimes this is too long, and the new Ebola vaccine is being administered in terms of “compassionate use” – it has yet to complete all its formal tests and paperwork, but it has been shown to be safe and effective. Something similar may be possible if one of the many groups around the world working on a vaccine for the new strain of coronavirus (SARS-CoV-2) is successful.
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