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One of the most promising coronavirus vaccine trials was halted due to a serious adverse reaction

Published Sep 9th, 2020 10:11AM EDT

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  • AstraZeneca confirmed that the Oxford vaccine’s Phase 3 trial was paused as it investigates the matter to determine what caused a serious adverse reaction in a volunteer in the UK.
  • A report says a patient developed a condition called transverse myelitis, an inflammatory syndrome that affects the spinal cord.
  • AstraZeneca has not confirmed the diagnosis, and it’s unclear whether the vaccine caused it.
  • The study might be resumed within a few days if regulators conclude that it’s safe to move forward.

Halting the spread of the novel coronavirus has been a daunting task for some countries, and a variety of factors hindered public health efforts to contain the virus. Vaccines could make it a lot easier for health officials to manage the pandemic and significantly reduce the spread, and immunization campaigns in the US might start before the end of the year. Several vaccine candidates have reached Phase 3 trials, with the final stage of testing now underway in the US, Europe, and other countries. Similar drugs are in Phase 3 trials in China and Russia, although those two countries have already issued emergency approvals for the vaccines even before safety and efficacy trials conclude.

Unfortunately, there are no guarantees that any of the advanced vaccine candidates will turn out to be effective and safe for public use. The recent debate around emergency approvals prompted nine companies to sign a pledge that says they will not cut corners during the trials, and only seek approval when the science can back up the drugs’ efficacy. Even promising vaccines can fail in Phase 3 trials, and we have seen other COVID-19 therapies fail to meet endpoints in human trials.

After months of tests, the first bad news concerning coronavirus vaccines comes from one of the frontrunners. AstraZeneca had to temporarily halt the Phase 3 trial of its Oxford vaccine because a volunteer experienced a major adverse reaction.

Stat was the first to report that the AstraZeneca trial is now on hold after a suspected adverse reaction in one participant in the UK.

AstraZeneca said in a statement that the company’s “standard review process triggered a pause to vaccination to allow review of safety data,” without offering any other details. The company said in a follow-up statement that it had halted the study on its own. Stat reported at the time that the nature of the adverse reaction was not known, but a person familiar with the matter said the participant in question will recover.

AstraZeneca said of the pause that it’s “a routine action which has to happen whenever there is a potentially unexplained illness in one of the trials, while it is investigated, ensuring we maintain the integrity of the trials.” The company is “working to expedite the review of the single event to minimize any potential impact on the trial timeline.”

A different source told Stat that the finding is having an impact on other AstraZeneca vaccine trials and other clinical trials.

It was The New York Times that offered additional details about the adverse reaction. A participant enrolled in a Phase 2/3 trial in the UK was diagnosed with transverse myelitis, an inflammatory syndrome that affects the spinal cord that can appear after viral infections. It’s unclear at this time whether the vaccine caused the adverse effect or whether it was something else that triggered it. The condition is treatable with steroids, which also happen to be useful against COVID-19.

Oxford scientists already described the side-effects of their drug in a study published in July following Phase 1/2 trials. They said volunteers experienced mild or moderate symptoms after inoculation, including muscle aches and chills. None of the reactions were severe or life-threatening, and they disappeared quickly.

The Oxford vaccine uses a modified chimpanzee adenovirus that is harmless to people. It incorporates coronavirus components that will then spark an immune response that could protect against a real infection with SARS-CoV-2, the virus that causes COVID-19.

Separately, BBC News reported this is the second time the AstraZeneca/Oxford trial has been put on hold since the first volunteers were immunized back in April. It’s unclear what caused the first pause, but such events are described as “routine.” Anytime a volunteer is admitted to the hospital and the cause of the illness is unclear, it triggers a halt in the trial.

The medical regulator in the country will soon decide whether it’s safe to restart the study, though the process could take a few days. Until then, AstraZeneca’s immunization campaigns that are part of the trials being conducted in the UK, Brazil, South Africa, and the USA are all on hold.

The event might seem disconcerting, but it’s also sobering. It reminds us that a COVID-19 vaccine candidate, no matter how promising, can always fail — it can either fail to elicit the desired immune response or cause other harm to volunteers. But this halt to the Oxford vaccine trial also shows how vital transparency is and how cautious pharmaceuticals companies had to be. It could even help alleviate concerns from the general public.

Chris Smith Senior Writer

Chris Smith has been covering consumer electronics ever since the iPhone revolutionized the industry in 2008. When he’s not writing about the most recent tech news for BGR, he brings his entertainment expertise to Marvel’s Cinematic Universe and other blockbuster franchises.

Outside of work, you’ll catch him streaming almost every new movie and TV show release as soon as it's available.

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