AstraZeneca pauses COVID-19 vaccine trials ‘to allow review of safety data’

By Rachel Arthur

- Last updated on GMT


Related tags Astrazeneca COVID-19 Vaccines

AstraZeneca has paused vaccination in all of its Oxford COVID-19 vaccine candidate trials globally, because of a potentially unexplained illness in one of the trials.

As a frontrunner in the race for a vaccine, the Oxford University AZD1222 vaccine candidate is in Phase 3 trials with up to 50,000 patients due to participate globally. Phase 3 trials started in the US just last week.

AstraZeneca says all trials have been paused globally as a routine response to an unexplained event. It highlights that in large trials illnesses will happen by chance, but must be investigated.

AstraZeneca: 'This is a routine action'

AstraZeneca has not released details on the nature, severity or location of the illness encountered during the trial.

“As part of the ongoing randomised, controlled global trials of the Oxford coronavirus vaccine, our standard review process was triggered and we voluntarily paused vaccination to allow review of safety data by an independent committee,”​ the company said in a statement sent to BioPharma-Reporter this morning.

“This is 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. In large trials, illnesses will happen by chance but must be independently reviewed to check this carefully. 

"We are working to expedite the review of the single event to minimise any potential impact on the trial timeline. We are committed to the safety of our participants and the highest standards of conduct in our trials.“

The independent committee reviewing the safety data will guide AstraZeneca on when trials could restart, with AstraZeneca pledging to continue work at the earliest opportunity. 

AstraZeneca’s COVID-19 vaccine candidate AZD1222 is one of the most advanced projects in the race to develop a vaccine. It entered a 30,000 people Phase 3 trial in the US last week: having already embarked on late stage trials earlier in the year in the UK, Brazil and South Africa. Further trials are also planned for Japan and Russia: with up to 50,000 participants due to participate globally.

AstraZeneca’s previously published timeline anticipated delivery of the vaccine could start by the end of the year. Its global supply capacity is to exceed 2 billion doses.

The vaccine is already lined up to supply a number of markets, subject to approval. This includes an agreement to supply 400 million doses to the US and UK, while an agreement with the European Commission last month also pledged the supply of up to 400 million doses. Other recent deals include 33.8 million doses for Australia.   

July study showed vaccine was 'safe and tolerated' 

AZD1222 uses a replication-deficient chimpanzee viral vector based on a weakened version of an adenovirus. It contains the genetic material of the SARS-CoV-2 virus spike protein. After vaccination, the surface spike protein is produced, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body.

The latest trial to launch – a Phase 3 trial in the US – involves adults aged 18 years or over from diverse racial, ethnic and geographic groups who are healthy or have stable underlying medical conditions, including those living with HIV, and those who are at increased risk of infection from the SARS-CoV-2 virus. Participants are randomised to received two doses of either AZD1222 or a saline control, four weeks apart. Twice as many participants receive the potential vaccine as the saline control.

In July 2020, interim results from the ongoing Phase I/II COV001 trial were published in The Lancet​ and showed AZD1222 was tolerated and generated robust immune responses against the SARS-CoV-2 virus in all evaluated participants.

The preliminary findings stated that the vaccine given as a single dose ‘was safe and tolerated... no serious adverse reactions occurred. The majority of adverse events reported were mild or moderate in severity, and all were self limited’.

The profile of these adverse events was similar to other ChAdOx1-vectored vaccines. The systemic reactions noted included fatigue, headache and muscle ache: with many reactions reduced with paracetamol.

Yesterday AstraZeneca's CEO was one of the nine signatories of a pledge from biopharma firms, in which the companies vowed to uphold the integrity of the scientific process as they work towards potential approvals of the first COVID-19 vaccines. Speaking to BioPharma-Reporter yesterday, AstraZeneca CEO Pascal Soriot said the company was "moving quickly but without cutting corners".

"We are putting science and the interest of society at the heart of our work," ​he said. "Regulators have clear and stringent efficacy and safety standards for the approval of any new medicine, and that includes this potential COVID-19 vaccine. We will remain true to our values as we continue our efforts to bring this vaccine broadly and equitably to billions of people around the world."

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