LONDON: The clean exit from the coronavirus pandemic promised by COVID-19 vaccines has been sullied by the arrival of new variants. Some of these viral newcomers appear to be putting up a fight against the current crop of jabs.
The scramble to update vaccines that have barely been rolled out is now pushing some towards a more ambitious goal: Universal “variant-proof” vaccines, able to fend off different varieties of the same virus family.
“Such pan-virus vaccines could be made in advance and deployed before the next emerging infection becomes a pandemic,” wrote Dennis Burton and Eric Topol from the Scripps Research institute in a Nature commentary last week.
“We call for an investment now in basic research leading to the stockpiling of broadly effective vaccines … Surely, global governments that together spend US$2 trillion a year on defence can find a few hundred million dollars to stop the next pandemic?”
VARIANTS PARTIALLY RESISTANT TO VACCINES
Many variants of SARS-CoV-2, the virus that causes COVID-19, behave no differently from their progenitors. A handful, though, appear able to partially resist the immunity conferred by vaccines.
The Oxford/AstraZeneca jab is less effective against the dominant coronavirus variant in South Africa than against the variant circulating in the UK, in terms of preventing mild to moderate disease (though, importantly, it is still believed to protect against severe disease and death).
The South African government has halted its rollout.
An unreviewed preprint suggests mRNA vaccines, like those from Pfizer and Moderna, might also see their potency dented by the mutations first detected in South Africa and Brazil.
The apparent drop in vaccine efficacy has arisen because COVID-19 vaccines are mostly designed to produce antibodies that bind to the virus “spike” protein, which latches on to human cells to infect them.
If mutations alter the spike protein sufficiently, antibodies can no longer “catch” the viral invader as effectively. These mutated viruses are less easily cleared from the body – and gain a survival advantage.
Now, the vision is to harness more generalised responders, known as broadly neutralising antibodies. These types of antibodies have been isolated from COVID-19 patients and found to also neutralise SARS-CoV-1, another virus in the coronavirus family responsible for severe acute respiratory syndrome, or SARS.
If they can quash several distinct coronaviruses, then they might also be able to combat current and future variants of the pandemic virus.
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THE CHALLENGE OF FINDING A UNIVERAL JAB
The challenge comes in finding a jab that produces these versatile antibodies. One starting point is to identify which parts of the virus remain unchanged as it mutates and then designing vaccines on the basis of these stable regions.
Researchers at the University of Nottingham in the UK are adopting this approach. While current vaccines target the S (spike) protein, they are gunning for both the S protein and the nucleocapsid, or N, protein.
The latter helps the virus to replicate and mutates more slowly than the spike protein. The scientists have teamed up with the company Scancell and Nottingham Trent University for a phase 1 clinical trial of its vaccine candidate, SN14.
The current jabs might also offer clues, according to Deborah Dunn-Walters, professor of immunology at the University of Surrey and chair of a COVID-19 task force.
“We will eventually have lots of different vaccines and some might be more tolerant of variants than others,” she says.
Those, she suggests, could be iterations along the road to a universal vaccine.
Alternatively, future COVID-19 vaccines could contain components targeting several variants, much as the seasonal flu jab features the three or four strains forecast to pose the biggest health risks.
The success of flu jabs depends on how well predictions match reality: Between 2009 and 2019, their effectiveness hovered roughly between 20 and 60 per cent.
Those underwhelming numbers, plus the pandemic potential of influenza, have spurred concerted efforts to develop a universal flu jab – without success. Two candidates flopped in clinical trials last year.
The search should continue. Flu is a notorious viral shape-shifter, more so than the virus that causes COVID-19. There have been three post-1918 flu pandemics: In 1957, 1968 and 2009.
As the light at the end of COVID-19 tunnel brightens, we should not discount other surprises coming down the track.
Listen to the behind-the-scenes considerations and discussions going into what might be Singapore’s biggest vaccination programme ever on CNA's Heart of the Matter podcast: