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Major pharma company pause trials for COVID-19 due to adverse effects

AstraZeneca with University of Oxford and in collaboration with various sites across the US who was working on a huge phase 3 clinical trial for testing Covid-19 vaccine has been put on hold due to some mysterious adverse reaction in a participant in the United kingdom.

The vaccine developed by AstraZeneca is known as AZD1222, where it uses a weakened version of common cold causing adenovirus, which is engineered to carry a gene coding for the spike protein in SARS-CoV-2 (COVID-19 causing virus) that is used to invade the cells. After vaccination the protein in the adenovirus induces the body's immune system to protect against the attack of SARS-CoV-2 if the individual is later infected. This model has been tested against other viruses like Ebola etc. but still experimental.

A statement released by AstraZeneca's spokesperson explained the company's standard review process forced to pause the trials to review all the data and its safety. They described that the pause was a regular action to whenever there is a possible mysterious illness while carrying out the trial, it is investigated to ensure the integrity of the trial is maintained.

The spokesperson also mentioned that the company is working to accelerate the review of every single participant's events to minimize any foreseen potential impact on the timeline of vaccines. They are doing so by running through the databases reviewed by as Data and Safety Monitoring Board, of other trials and looking for similar cases of adverse reactions

There can be a number of different reasons that can be quoted as serious unexplained adverse reactions, where symptoms require hospitalization, life-threatening illness and even death, but the nature of adverse reaction and how, when it occurred and its severity is not known but the participant is expected to recover, as per people familiar with this situation. It is also not clear in which clinical trial the adverse reaction occurred, where there is a possibility it could have appeared in the Phase 2/3 trial underway in the U.K. He also added the researchers have been told the hold on the trial was out of an abundance of caution.

The holds on clinical trials are common, but it's unclear how long it will last. But the pressure for it to be successful and to restrict the global pandemic and the media having a keen eye on the progress of every country’s vaccine updates, has sort of had an impact on the hold of the trial and out of the nine vaccine candidates who are in the 3rd phase of the trial, AstraZeneca is the first one who has put it in on hold which is also to be a thought of concern for the researchers.

AstraZeneca began its Phase 3 trial in the US, in late August, by enrolling 30,000 volunteers across 62 sites according to, a government registry, but some have not yet started enrolling participants. Phase 2/3 trials were previously started in the U.K., Brazil, and South Africa.

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