AstraZeneca resumes US COVID-19 vaccine trial; expects results later this year

By Rachel Arthur

- Last updated on GMT

All of AstraZeneca's COVID-19 vaccine trials are back in progress, following the green light from the FDA in the US. Pic:getty/yalcinsonat1
All of AstraZeneca's COVID-19 vaccine trials are back in progress, following the green light from the FDA in the US. Pic:getty/yalcinsonat1

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The US Food and Drug Administration (FDA) has given AstraZeneca the green light to recommence its Phase 3 COVID-19 vaccine trial in the US.

The trial was paused globally on September 6 after an unexplained illness in a study participant. While trials had recommenced in the UK on September 14 following the go-ahead from regulators (as well as in Brazil, South Africa and Japan in the following weeks) it was not until Friday [October 23] that the FDA gave the British-Swedish giant authorisation to recommence in the US.

“The FDA reviewed all safety data from trials globally and concluded it was safe to resume the trial,”​ said AstraZeneca on a statement on Friday.

Results anticipated later this year 

With all its trials now moving forward globally, AstraZeneca says results are anticipated later this year, depending on the rate of infection within the communities where the clinical trials are being conducted.

Data readouts will be submitted to regulators and published in peer-reviewed scientific journals. Rolling reviews of the vaccine program have already begun in countries where this regulatory pathway has been established, providing regulators access to data as soon as they become available.”

The European Medicines Authority (EMA) started a rolling review of AstraZeneca’s vaccine at the beginning of this month: marking the first COVID-19 vaccine to enter this process. This means that the committee has started evaluating the first batches of data from earlier trials.

“While trials are ongoing, AstraZeneca and Oxford University will continue to provide information to regulators, study investigators and participants according to clinical trial and regulatory standards,” ​adds AstraZeneca.

AstraZeneca: 'We should be reassured by the care taken by independent regulators'

AstraZeneca’s COVID-19 vaccine candidate – AZD1222 – uses technology from the University of Oxford and its spin-out company Vaccitech.

It uses a replication-deficient chimpanzee viral vector based on a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees and 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 Phase 3 trial has recruited more than 20,000 participants globally since it was launched. With the trials now fully resumed, AstraZeneca will now work towards reaching a total of 50,000 participants. (The US trial – funded by the Biomedical Advanced Development Authority (BARDA) - is the largest arm, covering 30,000 participants).

AstraZeneca highlights that in large scale vaccine trials it is not unusual for some participants to become unwell, and every case has to be evaluated to ensure the careful assessment of safety. It has not released the nature or severity of the illness that was encountered and resulted in the global pause.

Pascal Soriot, Chief Executive Officer, said: “The restart of clinical trials across the world is great news as it allows us to continue our efforts to develop this vaccine to help defeat this terrible pandemic. We should be reassured by the care taken by independent regulators to protect the public and ensure the vaccine is safe before it is approved for use.”

Viral vector candidates in the COVID-19 race

The Oxford University viral vector technology ChAdOx had already been used to produce candidate vaccines against flu, Zika and MERs. As soon as the genetic sequence for SARS-CoV-2 was published, scientists started applying the technology to a COVID-19 vaccine.

Johnson & Johnson’s vaccine candidate JNJ-78436735 (also known as Ad.26.COV2.S) is also a viral vector vaccine: using a human adenovirus to express the SARS-CoV-2 spike protein in calls with the company’s existing AdVac technology platform (used to develop and manufacture Janssen’s European Commission approved Ebola vaccine and construct its Zika, RSV, and HIV vaccine candidates).

Johnson & Johnson has suffered a similar setback with an unexplained illness resulting in a pause to its Phase 3 trial earlier this month. However, in a statement on Friday [October 23] the company said it was preparing to resume recruitment in the US.​  

CanSino’s vaccine candidate (Ad5-nCoV) also uses a non-replicating viral vector; as does the candidate from the Russia’s Gamaleya Research Institute (Gam-COVID-Vac).

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