AstraZeneca’s COVID-19 shot trials on hold after suspected reaction

Oxford and AstraZeneca’s COVID vaccine trial is put on HOLD for safety reasons after a British volunteer had a ‘serious’ reaction that could have been caused by injection

  • The AstraZeneca and Oxford University vaccine trials have been put on hold
  • A ‘serious adverse event,’ a possible reaction to the shot was reported in the UK 
  • Adverse event ‘serious’ if it requires hospitalization, or if it is life-threatening
  • The individual is expected to recover, but little else is known about their identity 
  • It is not clear if regulators, AstraZeneca or Oxford called for the trial hold
  • The Oxford University was dubbed the best hope for a vaccine by the WHO 
  • Had been hoped the vaccine could be rolled out in the ‘first few months’ of 2021

Phase 3 trials for the coronavirus vaccine being developed by Oxford University and AstraZeneca have been placed on a hold after a ‘serious adverse event’ was reported in a participant in the UK. 

Serious adverse events are suspected reactions to vaccines or drugs that require hospitalization, are life-threateningly or deadly. 

It’s unclear what the exact nature of the reaction was, but a person familiar with the matter told Stat News that the person is expected to recover. 

Trial holds are not uncommon, but it is a blow to worldwide hopes for a shot to be ready in the coming months, as the AstraZeneca shot was considered by many – including the World Health Organization – to be the leading candidate worldwide. 

The UK’s Health Secretary Matt Hancock said earlier this week he hoped it could be rolled out in the ‘first few months’ of 2021.

And Australia, for example, has spent $1.7 billion (US $1.24 billion) to secure access to a supply of 84 million COVID-19 vaccines, should the clinical trial be a success. 

Trials for AstraZeneca's shot are underway in the US, UK, Australia, Brazil (pictured) and other nations. Phase 3 testing will now be paused while safety data is reviewed

Trials for AstraZeneca’s shot are underway in the US, UK, Australia, Brazil (pictured) and other nations. Phase 3 testing will now be paused while safety data is reviewed 



The UK is the host of research and development efforts of the vaccine, which has been developed by researchers in Oxford and will be manufactured by AstraZeneca, a company based in Cambridge.

The British Government has ordered 100million doses of the jab and has already started manufacturing them so they’re ready to go if and when clinical trials are successful. The price paid has not been disclosed.


The US Government has ordered 100million doses of the vaccine and contributed $1.2billion (£910m) to the research and development of the jab.

European Union (EU)

The European Commission has agreed a deal for 300million doses of the vaccine if its clinical trials work, with the option to buy a further 100million. The deal has been made on behalf of countries in the EU. The amount of money spent is unknown. 


Australia has confirmed it ordered enough doses of the vaccine to give one to its entire population of 25million people. It is not clear how many doses the nation has ordered. The UK – with a population of 66m but an order of 100m – ordered more than it needs. 


One company in China has agreed a deal with AstraZeneca to make at least 100million doses of the vaccine.

Shenzhen Kangtai Biological Products, based in the city of Shenzhen, will increase capacity to 200m per year by the end of 2021.


A Russian company, R-Pharm, also has a deal to produce and distribute the vaccine, but it is unclear how many it will make or what it will pay to AstraZeneca.


Brazilian officials have set aside $360million (£274m) for at least 100million doses of the vaccine. Brazil is currently in one of the worst Covid-19 crises in the world with more than 3.6million official cases so far and 114,000 deaths.


Development of the AstraZeneca vaccine and eight others in phase 3 trials is being closely watched in the hopes they can stem the coronavirus pandemic that has killed more than 894,000 people worldwide, including nearly 190,000 Americans, and cost tens of millions their jobs. 

It comes after vaccine developers – including AstraZeneca – pledged not to cut corners on safety and efficacy testing, despite US President Trump’s urgent push for the Food and Drug Administration (FDA) to give emergency approval to a vaccine ahead of the November 3 election.  

‘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,’ an AstraZeneca spokesperson told

‘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.’  

AstraZeneca’s candidate vaccine, known as AZD1222, is in phase 3 trials – the final stage before safety and efficacy data can be submitted to regulators for approval – at dozens of sites across the US, and around the world. 

Along with Pfizer, and Moderna, AstraZeneca and its partner Oxford University had hoped to know whether the shot worked and was safe by year-end.

Mr Hancock said on Monday the UK’s ‘best-case scenario’ was to get the vaccine to the most-vulnerable patients within months, a timeframe that now appears less likely to be met. 

‘We have got 30 million doses already contracted with AstraZeneca,’ he said on UK radio station LBC.

‘In fact they are starting to manufacture those doses already, ahead of approval, so that should approval come through – and it’s still not certain but it is looking up – should that approval come through then we are ready to roll out.

‘The best-case scenario is that happens this year. I think more likely is the early part of next year – in the first few months of next year is the most likely.

‘But we’ve also bought vaccine ahead of it getting approved from a whole different series of international vaccines as well.’

More than 50,000 people worldwide had been taking part in ‘phase 3’ studies to see whether the Oxford jab can actually prevent people getting infected with Covid-19.

In these tests the vaccine is being given to tens of thousands of people in real-world environments to see if it stops them from catching Covid-19 in the community.

While trial holds to review safety data are not necessarily damning, the pause on AstraZeneca’s trial may very well delay the highly-anticipated results and completion of one of the fastest vaccine development pipelines in human history. 

The jab was expected at the end of 2020 but its creators have had to temper expectations after community transmission began to fizzle out in Britain and stall crucial trials needed to seal its approval

The jab was expected at the end of 2020 but its creators have had to temper expectations after community transmission began to fizzle out in Britain and stall crucial trials needed to seal its approval 

Phase 3 trials for the coronavirus vaccine being developed by Oxford University and AstraZeneca have been placed on a hold after a ‘serious adverse event’ was reported in a participant in the UK

Market confidence in the pharmaceutical giant took a hit as soon as reports of the trial hold emerged. 

Shares for AstraZeneca plummeted by eight percent in after-hours trading. 

President Donald Trump has hinted that he thinks a vaccine could be ready before a 'special date' - likely the November 3 election

President Donald Trump has hinted that he thinks a vaccine could be ready before a ‘special date’ – likely the November 3 election

The company is in now in mitigation mode to try to stay as close to its trial completion date as possible.

AstraZeneca is ‘working to expedite the review of the single event to minimize any potential impact on the trial timeline,’ the spokesperson told Stat News.   

Disconcerting though any signs that could suggest potential flaws in a leading vaccine for the disease that’s killed nearly 190,000 Americans is, the move to pause a trial over safety concerns may be reassuring to some. 

Hours before the trial was temporarily halted, AstraZeneca and eight other companies working on COVID-19 vaccines signed a pledge to prioritize safety of their shots over speedy development.  

They promised to ‘uphold the integrity of the scientific process as they work towards potential global regulatory filings and approvals of the first COVID-19 vaccine.’ 

The pledge was made in response to growing concerns that governments would press firms and research institutions to rush a vaccine through trials and approval processes in an effort to bolster political capital and restore normalcy amid the pandemic.  

Last week, the US Centers for Disease Control and Prevention (CDC) sent instructions to state health departments to prepare for the potential arrival of one of two coronavirus vaccines by the end of October. 

Subsequently, President Trump hinted at the hopeful possibility that a vaccine could be ready before a ‘special date,’ prompting speculation that he was referring to the November 3 presidential election – just days after the end-of-October potential finish line in the CDC guidance. 

Health officials like infectious disease expert Dr Anthony Fauci, US Surgeon General Dr Jerome Adams and Trump’s own vaccine czar Dr Moncef Slaoui were all quick to assure the American public that it was possible, but unlikely, that a shot would be ready by then, and that the FDA would pay no mind to the date, but only the data, to determine when a vaccine is ready for distribution. 

Pfizer, however, confirmed that it hoped to have sufficient trial data to know whether its shot was safe and effective by late October, and would submit for FDA approval ‘immediately’ afterwards. 

Most experts and observers speculate that the two unnamed shots referenced in the CDC guidance were Moderna’s and Pfizer’s, not AstraZeneca. 

The trial hold casts even further doubt over the possibility that the firm’s vaccine will be the first ready for the US market. 

Operation Warp Speed, the Trump administration’s effort to speed vaccine development, primarily by contributing funding to private companies working on shots, announced that AstraZeneca would be awarded up to $1.2 billion in funding for its vaccine development in May. 

The US has inked a deal with AstraZeneca for 300 million doses of its shot – if the vaccine is greenlit as safe and effective by the FDA – and had set its sights on an approval date as early as October, which seems increasingly improbable. 


1. GlaxoSmithKline and Sanofi Pasteur: 60million doses 

The Government revealed on July 29 it had signed a deal with pharmaceutical giants GlaxoSmithKline (GSK) and Sanofi Pasteur

If the vaccine proves successful, the UK could begin to vaccinate priority groups, such as frontline health and social care workers and those at increased risk from coronavirus, as early as the first half of next year, the Department for Business, Energy & Industrial Strategy (BEIS) said. 

Human clinical studies of the vaccine will begin in September followed by a phase 3 study in December. 

The vaccine is based on the existing technology used to produce Sanofi’s seasonal flu vaccine. Genetic material from the surface protein of the SARS-CoV-2 virus is inserted into insect cells – the basis of Sanofi’s influenza product – and then injected to provoke an immune response in a human patient.  

2. AstraZeneca (manufacturing University of Oxford’s): 100million

AstraZeneca, which is working in partnership with Oxford University, is already manufacturing the experimental vaccine after a deal was struck on May 17.

Professor Sarah Gilbert, who is leading the Oxford team, is confident the jab could be ready for the most vulnerable people by the end of the year.

Her comments came after the results from the first phase, published in The Lancet on July 20, showed promise.

The team have genetically engineered a virus to look like the coronavirus – to have the same spike proteins on the outside – but be unable to cause any infection inside a person. This virus, weakened by genetic engineering, is a type of virus called an adenovirus, the same as those which cause common colds, that has been taken from chimpanzees. 

3.  BioNTech/Pfizer: 30million 

US drug giant Pfizer – most famous for making Viagra – and German firm BioNTech were revealed to have secured a deal with the UK Government on July 20.

It reported positive results from the ongoing phase 2/3 clinical trial of one called BNT162b1 on July 1.  The company is still running phase 2 trials at the moment.

Pfizer’s vaccine is one called an mRNA vaccine, which do not directly inject bits of the virus into the body but send genetic material.

mRNA vaccines programme the body to produce parts of the virus itself by injecting the body with a molecule that tells disease-fighting cells what to build. The immune system then learns how to fight it.

4. Valneva: 60million 

The Government has given Valneva — whose vaccine is understood to be in the preclinical stages of development — an undisclosed amount of money to expand its factory in Livingston, Scotland. 

While the Government revealed a 60million dose deal on July 20, the company said it had reached agreement in principle with the UK government to provide up to 100million doses. 

Valneva’s jab is an inactivated whole virus vaccine, meaning it injects a damaged version of the coronavirus itself into the body.

The virus has been destroyed in a way that makes it unable to cause infection, but the body still recognises it as a dangerous intruder and therefore mounts an immune response which it can remember in case of a real Covid-19 infection. 

5. Janssen (Johnson & Johnson): 30million

The Government has agreed to buy 30million doses of a vaccine made by Janssen if it works.

Officials have agreed to help the company in its development of the jab by part-funding a global clinical trial. The first in-human trials of Janssen’s jab began in mid-July and are being done on adults over the age of 18 in the US and Belgium.

The jab is named Ad26.COV2-S, recombinant, and is a type of jab called a viral vector recombinant vaccine.

Proteins that appear on the outside of the coronavirus are reproduced in a lab and then injected into the body to stimulate an immune reaction.

The ‘Ad’ part of the vaccine’s name means it works using an adenovirus – a virus best known for causing the common cold – as a vehicle to transport the coronavirus genetics into the body.

6. Novavax: 60million

Britain has ordered 60million doses of a vaccine being developed by the US-based company Novavax. It will help to fund late-stage clinical trials in the UK and also boost plans to manufacture the vaccine in Britain.

Novavax’s jab, named NVX-CoV2373, showed positive results in early clinical trials.

It produced an immune response in 100 per cent of people who received it, the company said, and was safe and ‘generally well-tolerated’. 

Novavax’s candidate is also a recombinant vaccine and transports the spike proteins found on the outside of the coronavirus into the body in order to provoke the immune system. 

7. Imperial College London: Unknown quantity

Imperial College London scientists are working on Britain’s second home-grown hope for a jab. The candidate is slightly behind Oxford’s vaccine in terms of its progress through clinical trials, but is still a major player.

The UK Government is understood to have agreed to buy the vaccine if it works but details of a deal have not yet been publicised. 

Imperial’s jab is currently in second-phase human trials after early tests showed it appeared to be safe. 

Imperial College London will try to deliver genetic material (RNA) from the coronavirus which programs cells inside the patient’s body to recreate the spike proteins. It will transport the RNA inside liquid droplets injected into the bloodstream.