Singapore scientists pursue booster vaccine to counter Covid-19 variants, other coronaviruses
- A study found that Sars survivors fully vaccinated with Pfizer-BioNTech developed antibodies that could neutralise variants and other coronaviruses that could be contracted by humans
- Scientists say this could be the basis of a booster vaccine to control the current pandemic and prevent the next one, and want to recruit more Sars survivors for their research
Professor Wang Linfa from the Duke-NUS emerging infectious diseases programme, one of the study’s authors, said the findings were key for the development of next-generation vaccines that would not only help with controlling the current pandemic “but may also prevent or reduce the risk of future pandemics caused by related viruses”.
Before receiving Covid-19 vaccinations, the Sars survivors only had antibodies against the disease they recovered from. The Sars-CoV-1 virus that causes Sars shares an overall genome sequence identity of almost 80 per cent with the Sars-CoV-2 virus causing the Covid-19 disease.
Wang said the “eureka moment” during the study came when those who had recovered from Sars and were jabbed with the Pfizer vaccine showed uniform high-level cross-neutralising antibodies against 10 different sarbecoviruses. These are a subgroup of coronaviruses – including the ones that caused Sars and Covid-19 – with the potential to jump from animals to humans and potentially start the next pandemic.
By comparison, those who had never been ill with Sars or Covid-19 and were vaccinated against the latter showed antibodies against the virus that causes Sars, but the levels were “not good enough”, Wang said. Those who recovered from Covid-19 had higher levels of antibodies after getting jabbed than those who had not contracted either disease, but their Sars antibodies were still not very high.
The study, published in the influential New England Journal of Medicine on August 18, was conducted this year with 28 people – eight Sars survivors, 10 healthy people who had not contracted Sars or Covid-19, and 10 who had recovered from Covid-19.
The immune responses of all 28 were compared before and after they received two doses of the Pfizer-BioNTech vaccine, which uses Messenger RNA (mRNA) technology to provide human cells with the genetic instructions to make a harmless surface protein of Covid-19. This protein then trains the immune system to recognise and build a response against the actual virus.
Covid-19 was first identified in the Chinese city of Wuhan in late 2019, but scientists have not yet been able to identify the source of the virus or how it spread, which could help them prevent a future coronavirus-fuelled pandemic.
Wang from Duke-NUS and the team of researchers across medical schools and hospitals in Singapore have a name for the potential third-generation vaccine: 3GCoVax.
The current first-generation vaccines offer varying levels of protection against Covid-19, but their efficacy is lower against new variants of the virus, especially the highly contagious Delta variant.
Several second-generation vaccines that can protect against the original strain, current variants and other human-infective coronaviruses are being developed. Scientists are also concerned that new, deadlier variants will emerge that could render current vaccines ineffective.
Said Wang: “I think it’s the first time in the history of mankind that – if everything goes according to the World Health Organization’s plans – by this time next year, the majority of the global population will be vaccinated against Sars-CoV-2. So if we boost that population with 3GCoVax, we also potentially can be ready to fight and prevent the next pandemic.”
He added that there were already “several companies at the contract stage” who were interested in building on these findings to make such a booster vaccine.
Wang – one of the world’s leading experts in zoonotic diseases, bat immunology and pathogen discovery – said the team was also keen to create broad neutralising antibodies for therapy, apart from developing 3GCoVax.
They are looking to recruit more people who have recovered from Sars, as he is hopeful that Sars survivors will also show the same antibody response after receiving vaccines made by AstraZeneca or Sinovac.
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Wang said he was keen to study those in mainland China, Hong Kong and Canada, where there were larger cohorts of Sars survivors.
The Sars epidemic of 2003 infected more than 8,000 people around the world, resulting in at least 774 deaths. Hong Kong was badly hit, with a total of 1,755 cases and 299 deaths; mainland China had 5,327 cases and 343 deaths; while Canada had 438 cases and 44 deaths.
“My hypothesis is that [the other vaccines will produce the same effect with Sars survivors]. But as a scientist, you know, you don’t trust your hypothesis only, you need the real data,” he said.