May 19 (SCMP) – As countries race to vaccinate their populations against the coronavirus and its variants, some scientists have turned their focus to a broader goal: a vaccine that protects against a range of coronaviruses, even those that have yet to emerge.
Researchers at the Duke Human Vaccine Institute (DHVI) in the United States say they have taken a critical step towards such a super-jab.
Their “nanoparticle” vaccine can trigger an immune response not only to the coronavirus that causes Covid-19 and several of its variants, but also to the Sars virus and related coronaviruses found in bats, according to findings published in the journal Nature last week.
The findings – based on animal tests – could have an impact on controlling the Covid-19 pandemic, the researchers say. The nanoparticle vaccine blocked monkeys from getting infected with the Sars-CoV-2 virus, which causes Covid-19. It also provoked a stronger immune response, with higher levels of virus-fighting neutralising antibodies than seen with current vaccines.
That suggests the vaccine, if approved for humans, could be used as a booster shot to enhance immunity and counter new variants of the virus in the future, according to the researchers.
But it may also have more far-reaching implications for what some scientists call the current “pandemic age” – where the risks of animal viruses crossing into people and causing outbreaks are growing alongside expanding human populations and land development.
“We’ve had two major [coronavirus] outbreaks before Covid-19, one in 2003, the Sars outbreak, and another in 2011, the Mers outbreak … and certainly we expect there will be others,” said Bart Haynes, DHVI director and one of the developers of the nanoparticle vaccine.
“Now is the time to provide the vaccines that will prepare for those, so that we can control outbreaks and keep them from becoming pandemics in the future,” he said.
The idea is to create a vaccine that will work not just against a coronavirus currently in circulation, but that could also protect against the scores of known and unknown viruses that are circulating in animals like bats and could be able to infect people.
The concept of a “pan-coronavirus” vaccine has long been a dream of emerging infectious disease specialists, and now, as the Covid-19 pandemic has sickened millions and ground economies to a halt, the idea is gaining significant attention.
Like other Covid-19 vaccines, this one works by targeting a section of Sars-CoV-2 that enables it to bind to human cells.
However, the researchers chose a section that is not just present in Sars-CoV-2 and circulating variants, but is also found in the Sars virus and related bat viruses that have not spilled into people.
By using an area found across multiple coronaviruses the vaccine was able to trigger neutralising antibodies against a range of viruses, when tested in the blood of vaccinated monkeys.
When compared with a substitute mRNA vaccine researchers said was analogous to those already in use, the new vaccine created a stronger response to variants of the virus identified in South Africa and Brazil. These variants are thought to have some ability to evade vaccines currently in use.
But the significant finding for the future was that it provoked an immune response against two coronaviruses found in bats, as well as the Sars virus, although they were not as strong as against Sars-CoV-2.
Immunologist Kylie Quinn, who was not involved in the study, said that while creating a vaccine to cover all coronaviruses was a “big ask”, it was certainly feasible that the Duke team’s approach could create a vaccine with broad protection against a subgroup of coronaviruses.
The comparatively high level of antibody responses that their vaccine was able to elicit against Sars-CoV-2 and its variants boded well for how it might cover similar viruses, according to Quinn, a vice-chancellor’s research fellow at RMIT University in Australia.
“Even if you had just a modest level of protection, it could be enough to convert [an infection from a new coronavirus] from something which is a very severe illness to something which is less severe, and that gives us an advantage,” she said.
The researchers also stressed that the findings do not mean that the vaccine – if eventually found safe for humans – would protect against all coronaviruses lurking in nature, most of which have yet to be identified and catalogued by scientists.
For example, the current formulation does not provoke an immune reaction to the virus that causes Mers, which is more genetically removed from the viruses that cause Sars and Covid-19.
But lead author Kevin Saunders, director of research at the institute, said he felt “optimistic” the vaccine would work against coronaviruses that were closely related to Sars.
Meanwhile, the vaccine platform, which arms a tiny particle with a repeating version of the part of the virus needed to provoke immunity, is easily adaptable for other viruses.
“We can just make some small tweaks to it, by interchanging some pieces. That then will broaden it to be able to interact with the Mers-like viruses,” Saunders said. “[With this platform] we do have a fairly good chance of coming up with a really broad and effective vaccine.”