When a needle was plunged into his arm in mid-April, 18 year-old Zang Weiye became the youngest man in China to be given a trial vaccination against the novel coronavirus. He was reported to be suffering a slight fever and fatigue after the inoculation but the reaction had largely disappeared the next day.
“I trust scientists,” the Wuhan University student explained of his volunteering for the trial, despite initially hiding the decision from his more conservative family.
It would be difficult for Zang to keep things completely secret. The injection he was given – known as Ad5-nCoV – is currently the only vaccine candidate that’s into the second phase of clinical trials – a stage that aims to test the contender’s efficacy in shielding the human body from SARS-CoV-2, the virus that causes Covid-19.
According to its developers – Tianjin-based CanSino Biologics and China’s Academy of Military Medical Sciences – Ad5-nCoV is designed to trigger the production of antibodies through presenting a harmless, genetically-engineered adenovirus that expresses SARS-CoV-2’s spike protein (the key feature responsible for getting the virus into mammalian cells).
CanSino’s Ebola vaccine, which was approved by the Chinese government in 2017, was created with a similar methodology.
Sanofi and GSK, two of the world’s largest pharmaceutical companies, are engaging in “unprecedented” collaboration to produce a vaccine of their own against SARS-CoV-2, with some 86 other Covid-19 vaccine projects also in process around the world, according to Faster Cures, a US think tank that focuses on accelerating medical research.
Six have moved into various stages of clinical trials, of which three originate in China.
The Wuhan Institute of Biological Products, an affiliate of state-owned Sinopharm Group, and Sinovac, a Beijing-based biotech company partnering with California-based Dynavax Technologies, are the other two developers testing their vaccines on humans. Both use inactivated virus particles to trigger an immune response in the body – an approach already adopted in existing vaccines against hepatitis A, influenza, polio and rabies. However, inactivated vaccines generally can’t induce strong immunity, meaning that people need booster shots over an extended period to maintain effective protection.
Include the tie-up between Beijing Advaccine Biotechnology and Inovio Pharmaceuticals from the US (the latter is sponsored by the Bill and Melinda Gates Foundation) and China has stakes in four of the six vaccines on trial.
That duo is adopting the same route pursued by US government-backed Moderna Therapeutics, which was first to launch a clinical trial for a Covid vaccine and created the first clinical batch just 25 days after the viral genome was sequenced in China in January.
Rather than injecting proteins or viral particles, Moderna’s experimental drug employs messenger RNA (mRNA) that triggers cells to produce the viral proteins that provoke an immune response.
Germany’s BioNTech, Pfizer and Shanghai Fosun Pharmaceutical are also joining forces to develop an mRNA-based vaccine. Innovative as it seems, the approach belongs to a new class of nucleic-acid vaccines that has yet to be licenced for human use anywhere in the world.
To speed up the creation of a vaccine, Chinese scientists have explored all five mainstream approaches for vaccine development since February, which explains why the country has such a large number of runners in the race. However, there is no guarantee that any of these projects will yield practical results. And even if they do, it could be another 18 months before the first batch of Covid-19 vaccines become available for public use, partly because of the difficulty of readying production capacity before final identification of an approach that works best. (The UK government is taking a slightly different tack in this regard – it says that a vaccine being developed by Oxford University could be ready by September and that it is willing to risk going into production before it is 100% certain it will work. Sarah Gilbert, the lead scientist on the project, says she is 80% certain the vaccine will be effective, despite “five years of work being compressed into four months”, The Times reports.)
Adding to the challenge is the changing nature of SARS-CoV-2. More than 33 mutations of the virus have already been identified, according to research published last week by Li Lanjuan, the first scientist to propose the Wuhan lockdown. Using “ultra-deep sequencing” the research team from Zhejiang University found that the most aggressive strains could generate 270 times the viral load of the weakest types. Dominant strains also vary by geographic region. “Drug and vaccine development, while urgent, needs to take the impact of these accumulating mutations … into account to avoid potential pitfalls,” Li warned.
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