AstraZeneca & Oxford University Suspend COVID-19 Vaccine Trial To Investigate Potential Severe Adverse Reaction
Transmission electron micrograph of SARS-CoV-2 (red), the virus that causes COVID-19

AstraZeneca on Tuesday night suspended the Phase 3 trial of their experimental COVID-19 vaccine in order to investigate a a suspected severe adverse reaction in a volunteer reported in the United Kingdom.

The trial suspension follows just on the heels of AstraZeneca’s chief executive officer’s pledge to seek regulatory approval for a COVID-19 vaccine only after it has been proven to be safe and effective in large, randomized Phase 3 clinical trials. AstraZeneca’s CEO, along with the CEOs of eight other companies at the forefront of coronavirus vaccine development, signed the pledge on Tuesday.

“At AstraZeneca we put science, safety and the interests of society at the heart of our work. This temporary pause is living proof that we follow those principles while a single event at one of our trial sites is assessed by a committee of independent experts,” CEO Pascal Soriot said in press release. “We will be guided by this committee as to when the trials could restart, so that we can continue our work at the earliest opportunity to provide this vaccine broadly, equitably and at no profit during this pandemic.”

The pause is a sign that pharmaceutical companies are taking seriously routine clinical trial protocols to stop trials in the case of severe adverse reactions, even as pressure builds to get a safe and effective vaccine to market as soon as possible. Russia and China have already approved investigational COVID-19 vaccines for limited use, ahead of the completion of Phase 3 trials.

The Trump administration has indicated it’s looking to roll out a COVID-19 vaccine for wider use in late October, just ahead of the US presidential election on November 3rd. On Wednesday, the Administration issued new guidance to allow pharmacists and pharmacists in training to administer the vaccine, in preparation for a successful vaccine’s roll-out.

The World Health Organization and independent health experts have cautioned against prioritizing speed over safety; and are concerned that political pressure will lead to wider deployment of an investigational vaccine before large, final-phase trials have proven the vaccine to be safe and efficacious. It is unlikely that Phase 3 trial results will be available before early 2021.

Participant Who Experienced Suspected Adverse Reaction Is Doing Well

The trial was suspended because one participant was diagnosed with transverse myelitis – an inflammatory condition of the spinal cord that can be brought on by viral infections – according to the New York Times. However, it’s still unknown whether the condition was related to the investigational COVID-19 vaccine, although Soriot confirmed in a private call with investors that the patient had been enrolled in the arm that received the COVID-19 vaccine. However, he also told investors that the patient is doing well and will likely be released from the hospital as early as today, according to STAT News.

Such pauses are not uncommon, according to the director of the US National Institutes of Health Francis Collins.

“To have a clinical hold, as has been placed on AstraZeneca as of yesterday, because of a single serious adverse event is not at all unprecedented,” Collins told a Senate panel on Wednesday. “This certainly happens in any large-scale trial where you have tens of thousands of people invested in taking part, some of them may get ill and you always have to try to figure out: Is that because of the vaccine, or were they going to get that illness anyway?”

However, Collins added that should the review of the safety data find that the adverse event was related to the vaccine, all doses already manufactured would be disposed. The Trump administration signed a deal in May with AstraZeneca to produce 300 million doses of their investigational vaccine by January 2021, to be ready for mass rollout should the vaccine prove to be safe and effective.

“This ought to be reassuring to everybody listening when we say we are going to focus first on safety and make no compromises,” said Collins.

The massive trial – which has enrolled participants in dozens of study sites across the United Kingdom, Brazil, South Africa, and the United States – is one of the largest Phase 3 trials currently underway in the COVID-19 vaccine race, and the length of the trial’s suspension has not been confirmed. However, sources familiar with the trial told the Financial Times that the trial may resume in the next week.

Novel Technology Put To The Test In COVID-19 Vaccine Trials

In the private call with investors on Wednesday, Soriot also confirmed that the trial had been paused once in July due to a suspected adverse reaction. It resumed shortly after the suspected case was cleared to not be related to the vaccine candidate.

The vaccine, AZD1222, was co-developed by the University of Oxford, and uses a weakened version of a chimpanzee adenovirus – a common cold causing virus – to carry the genetic material of the SARS-CoV-2 spike protein. Once injected, cells inside the body produce the spike protein, a harmless but discrete marker of the SARS-CoV-2 virus, priming the immune system to recognize the virus and attack if the body is later infected.

There is no licensed vaccine with an adenovirus backbone on the market yet. However, this is in large part due to the novelty of the technology, according to Barry Bloom, an infectious disease epidemiologist and former dean of Harvard School of Public Health.

“No one had the genetic tools to be able to make them and make them quickly. So, the revolution in molecular biology and genetics and the ability to replace one gene with another rapidly easily and effectively, and has really speeded things up tremendously,” Bloom told Health Policy Watch. 

So far, results from a Phase 1/2 trial of the AstraZeneca/Oxford vaccine candidate published in July found that in 1,000 people, about 60% experienced “mild or moderate” symptoms after vaccination. These symptoms included pain at the injection site, feeling feverish, chills, muscle aches, and malaise. In that trial, no serious adverse reactions were reported.

Image Credits: NIAID.

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