The suspended testing of a leading experimental coronavirus vaccine in Britain is unlikely to affect Hong Kong’s procurement plans for shots, as many other candidates were in the final clinical phase, according to a government health adviser.
Professor David Hui Shu-cheong of Chinese University noted that the vaccine being developed by AstraZeneca in partnership with Oxford University was just one of nine in late-stage trials.
“It’s always common to have some problems during phase three clinical trials in which a vaccine is tested on more than a 100,000 people,” Hui said. “Only those companies that can survive till the end will win.”
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Hui is a member of the government’s scientific committee on vaccine-preventable diseases, responsible for tracking candidates in the final stage of development around the world.
Hong Kong has adopted a two-pronged approach to securing shots. Apart from buying directly from the manufacturers, the government has joined the global Covax Facility procurement mechanism managed by the World Health Organisation (WHO) and two other platforms, Gavi and the Coalition for Epidemic Preparedness Innovations. The programme is aimed at avoiding “vaccine nationalism” whereby wealthy countries snap up all doses once they become available.
AstraZeneca, which has agreed to provide almost 3 billion shots to governments across the globe, said on Tuesday it had halted late-stage trials after a participant experienced “an unexplained illness”.
The company has not clarified beyond that point, saying only there had been no final diagnosis in the case and an independent committee would carry out a review.
But according to the director of the United States National Institutes of Health, Francis Collins, the adverse reaction was transverse myelitis, a neurological disorder that causes inflammation of the spinal cord.
The woman’s situation has improved and she is expected to be discharged from hospital, according to STAT, an American news website focused on health.
AstraZeneca told British media on Thursday a vaccine could still be available by as early as December, despite the randomised clinical trial being paused.
“We could still have a vaccine by the end of this year, early next year,” chief executive Pascal Soriot said at a media event.
Hui emphasised that the delay would not hinder Hong Kong’s plans to secure supplies of shots.
“The battlefield in vaccine development is very keen, and with more companies entering the phase three trial; it depends on whether there will be enough volunteers globally to participate,” he said. “But at this moment, there will not be much impact to Hong Kong’s procurement even if one of the vaccines fails. For AstraZeneca, if investigation proves the adverse effect was not caused by the vaccine, it can continue with the trial.”
Hui noted that apart from the nine leading candidates, 26 others were about to enter the clinical trial phase.
“The WHO basket will cover more than one vaccine in the end and will include those which can complete phase three and are reportedly safe and stable,” Hui said. “Some vaccines could be available, at the earliest, by the end of November or early December.”
The government had reserved enough shots through the WHO programme to initially cover about 35 per cent of the city’s 7.5 million residents, he said.
Undersecretary for Food and Health Dr Chui Tak-yi agreed AstraZeneca’s delay was not unusual.
“The third phase of clinical testing is a necessary process for large-scale international drug research to see … any negative effects,” Chui said. “It is normal during the development process that a suspension may occur if there are some side effects, and to find a third party to investigate thoroughly before continuing the trial.”
The government would provide further details on its procurement of vaccines when the information became available, he said
Professor Yuen Kwok-yung, a top infectious disease expert at the University of Hong Kong and an adviser to the government on its pandemic response, offered assurances it was common for participants in vaccine trials to suffer side effects.
“This is a completely new vaccine that has never been tested on people, so we are not able to predict what side effects it could have,” Yuen told a radio programme on Thursday. “That’s why vaccine trials go through three stages, with increasing numbers of people.”
Adverse reactions usually appear only at the final stage, when tens of thousands of people are taking part, and stopping a trial is a normal part of the process, according to Yuen.
“While we have to be careful going forward, this does not mean we will lose confidence in the vaccine,” he said.
The Oxford trial includes 17,000 participants in Britain, Brazil and South Africa, with half receiving the main vaccine candidate and the rest a comparison, according to an article the team posted on the Conversation website. Late-stage testing began in the US in August and AstraZeneca plans to eventually enrol up to 50,000 volunteers worldwide.
The other eight leading candidates are being developed by four Chinese companies and firms from Russia, the US, Germany and Australia.
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