In the past few days, two main variants first identified in India have crowded Australian newspapers’ headlines. These are the B.1.617.1 – or Kappa, according to the new nomenclature released by the WHO – and the B.1.617.2, or Delta.
Like the variants first identified in the UK (Alpha, or B.1.1.7), South Africa (Beta, or B.1.351) and Brazil (Gamma, or B.18.104.22.168), the strains detected in India last October all have spike protein mutations that have been associated with increased transmissibility.
Variants of SARS-CoV-2 become of interest or concern when they exhibit higher viral load, extended periods of shedding, or an improved binding ability to the ACE2 receptor in human cells, making them more transmissible, more virulent, and capable of escaping the immune response.
The Kappa variant is the culprit of the latest Melbourne outbreak. It may have atypical clinical presentations, such as abdominal pain, nausea, vomiting, diarrhea and hearing impairments, but it’s not the most infectious variant of those that emerged in India. Most experts agree that its transmissibility is only equal, if not inferior, to Alpha.
“Delta is even more dangerous,” says Associate Professor Hassan Vally, an epidemiologist at La Trobe University. “It looks to be not only more infectious but probably more virulent.”
Preliminary reports from the UK, where Delta is quickly replacing Alpha in community transmission, indicate that Delta is about 50% more contagious than Alpha, which is already 52% more contagious than the original virus.
“Being more infectious means that potentially more people catch it. And if more people catch it, more people get hospitalised, and more people may die,” says Vally.
Besides transmissibility and virulence, one of the main concerns is whether these new variants are susceptible to currently available vaccines. Early data from the UK seem promising.
A recent study, yet to be peer-reviewed, showed that Pfizer and AstraZeneca provided a level of protection against Delta that was similar to that against Alpha.
“We’re still learning about these new variants,” Vally points out. “They are new, and the information that we have is still limited.”
Meanwhile, news has reported a “hybrid” variant recently identified in Vietnam, which is deemed a combination of Alpha and Delta.
Vietnam has successfully contained the virus for most of last year thanks to an aggressive strategy of early screening of passengers at airports and a strict quarantine and monitoring program. But the country has been grappling with a spike in infections since late April – yet another reminder that a COVID-zero policy is not sustainable in the long term and that a fast, global vaccination campaign is essential to protect populations from emerging variants.
“A COVID-zero policy is not sustainable in the long-term,” says Associate Professor James Wood, an epidemiologist and mathematician at the School of Public Health and Community Medicine at the University of New South Wales. “[The pandemic] is not controlled in all parts of the world, which means our risk persists.”
Wood anticipates that countries that have not adopted a COVID-zero policy but are well ahead with vaccination, such as the UK, will begin to see a significant reduction in cases and severity of the disease. “Our opinion will start to change then,” he says.
While an almost COVID-free country has meant that the life of most Australians has gone on with some kind of normality, there are a lot of things we’re giving up. Travel restrictions have kept families apart for more than a year. Australians have died in India as a result of travel bans. The economy is suffering.
Living in an almost COVID-free country has also shifted our benefit-versus-risk perception regarding vaccination.
“Having a low risk from COVID itself and a well-publicised rare risk [associated with AstraZeneca] has contributed to hesitancy,” says Wood.
Encouragingly, Melbourne vaccination hubs have been significantly busier since the last outbreak ignited.
“Maintaining COVID-zero means that you cannot be complacent until you have the population immune through vaccination,” says Vally. “This virus will exploit any gap in your defences. And of course, now we’ve got other strains that are even better at exploiting any opportunities to spread.
“You cannot drop your guard, and it’s really important for us to get vaccinated.”
|Name (Pango lineage)||Name (WHO)||First Detected||Transmissibility||Virulence||Immune escape|
|B.1.1.7||Alpha||United Kingdom September 2020||About 50% increased transmission compared to the original virus||Potential increased severity based on hospitalisations and case fatality rates||Minimal impact on neutralisation by convalescent and post-vaccination sera|
|B.1.351||Beta||South Africa May 2020||About 50% increased transmission compared to the original virus||Significantly reduced susceptibility to some treatments||Reduced neutralisation by convalescent and post-vaccination sera|
|B.22.214.171.124 (P.1)||Gamma||Brazil November 2020||Estimated transmissibility is 1.4–2.2 times more than other lineages.||Significantly reduced susceptibility to some treatments.||Reduced neutralisation by convalescent and post-vaccination sera|
|B.1.617.2||Delta||India October 2020||Estimated 50% more transmissible than B.1.1.7||Potentially reduced susceptibility to some treatments||Potentially reduced neutralisation by convalescent and post-vaccination sera|
|B.1.617.1||Kappa||India October 2020||Transmission at least equivalent to B.1.1.7||Potentially reduced susceptibility to some treatments||Potentially reduced neutralisation by convalescent and post-vaccination sera|
Dr Manuela Callari is a Sydney-based freelance science writer who specialises in health and medical stories.
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