Special investigation: COVID experts warn variant threat can only be beaten by worldwide vaccination

The Delta strain of COVID-19 is the most contagious variant of the disease to date, but experts warn we will continue to see even more transmissible — and potentially more deadly — versions emerge. For as long as there are unvaccinated populations in the world, there is fuel for SARS-CoV-2 to evolve and mutate. Renowned American epidemiologist Larry Brilliant, who is credited with playing a major role in the eradication of smallpox, is the founder and chief executive of Pandefense Advisory, a network of world-class experts urgently engaged in pandemic response. Dr Brilliant believes there’s a good chance we won’t reach herd immunity. “The threshold for herd immunity is when, on average, one case is able to infect fewer than one other case. It’s a math equation: Herd immunity means the effective reproductive number — R — is less than one. In that case, the pandemic fritters out. But with every new variant that is successful, R increases, crowding out the incumbent,” he recently explained in Wired magazine. “The whole reason we’re rushing to vaccinate everybody is to get people protected against this disease, so that when we do get variants that are more lethal, we will be able then to simply get booster doses. These vaccines clobber today’s variants, but they can’t clobber tomorrow’s, because we just don’t know where this wily virus is going to mutate and become a variant. “We’re all customers for the virus ... Think about the pandemic in year three or four. There will still be billions of people unvaccinated. Billions of people will harbour billions of viruses. Each one will be replicating. A certain percentage will mutate. A certain per cent will become variants of those variants — some will be of high concern, and a percentage will be f...ing nightmarish.” Australian scientists agree the virus will continue to find ways to “escape immunity” and only vaccination will obstruct its spread and modification. University of WA virologist Associate Professor Allison Imrie said the more unvaccinated people there were, the more opportunity the virus had to evolve. “All of us people have different immune systems and different states of health, so there’s all this extra capacity for the virus to continue to evolve,” she told The West Australian. “So it will continue to do that. That is one thing we can be certain about. What’s harder to predict is exactly how virulent the virus will become. “We can just discuss that, but we don’t know for certain. Viruses evolve to escape immune pressure. That’s how viruses work. So when the virus enters a new host, it can modify slightly. And it continues to do this as it moves through more people. “And that’s how we’ve seen this evolution of so many variants, and some of them are more significant than others. They’re the ones that are called variants of concern. This most recent one (Delta) appears to be much more infectious based on the epidemiological evidence.” Another virologist, Professor Stuart Turville of the University of NSW’s Kirby Institute, talks about “fitness gains” when describing the evolution of the virus, likening it to an athlete growing ever stronger. “In populations that aren’t vaccinated it will go in a direction in which it will just become fitter and bind to the cells better ... it’s kind of grabbing on to something really tight, and then just grabbing on to it tighter and tighter like a wrench,” he said. “The worst case scenario — look it has the potential to do it — is that it can fitness gain and evade antibodies as well. “It’s done it with the variants like the Beta (strain), which was colloquially referred to as the South African variant. That is the variant we need to look out for, one that can not only infect really well but kind of reduce the potency of the current vaccines that we’ve got. “We will need to have updated (vaccine) formulations moving forward to tackle those.” “A virus becoming fitter is one thing. A virus becoming fitter and more deadly is another we’ve got to look at moving forward.” He said it was the “$6 million question” for experts right now. The United States’ top public health official, Dr Anthony Fauci, has called the Delta strain the “greatest threat” to his nation’s efforts to get back on its feet, even though 47 per cent of Americans are fully vaccinated. In the UK, which is opening up again with half its population fully vaccinated, the Delta variant has reversed the trend of decreasing deaths and hospitalisations. It is already the dominant strain there and preliminary evidence from England and Scotland indicates those infected are about twice as likely to end up in hospital. People need two doses of the vaccines to be protected from Delta, also known as B.1.617.2. It explains why Delta is being taken very seriously in Australia, with a big part of the country currently locked down to stop the variant getting a foothold. With only 5.8 per cent of the country fully vaccinated, Australia offers perfect conditions for the virus, like a tinder-dry native forest to a lit match. Delta was first identified in India, where it ravaged the sub-continent, killing hundreds of thousands of people. Another, even more dangerous mutation, Delta Plus, has reached the UK and US. Professor Turville said scientists like himself, tracking the new variants, were “learning in real time”. He said SARS-CoV-2 has “a bag of genetic tricks” keeping them on their toes. “It is a large virus in terms of its genetic capabilities, it’s three times the size of the gene in the HIV,” he said. “So it’s got a lot of things it can do if it gets into our body. But we’re still learning and some of them change things ... So all of these genes, in addition to the way it sticks to cells, they kind of manifest in our bodies, to do different things.” It’s not all grim and foreboding tidings. “Delta is supplanting the other variants,” he said. “The good news is, it’s vaccine targetable. The vaccines work really well against this variant. You need those two doses to get that coverage. “What (Delta) might actually do is flush out the (variants) that evade the immune response, like Beta, the one from South Africa.” That is happening in South Africa, where Delta is accelerating. Professor Turville’s laboratory gets to check out all new variants. “The way that my lab works ... we’re kind of a sentinel network, where we’re looking at things carefully as they come in,” he said. “So a virus will come into quarantine, we’ll get it, we’ll grow it, we’ll test it against anybodies from somebody that’s vaccinated, and we will know very, very quickly whether that virus is susceptible to the vaccine response, or whether it’s completely evaded it, or it’s taken the edge off that vaccine response. “There’s no (strain) we have found yet that completely evades the vaccine response. So that’s good news.” The current vaccines were designed to prevent serious disease and death, rather than infection. The viral load was less in those who have had their jabs, making them less likely to cough it over somebody else, Professor Imrie said. “Although they may not suppress replication of the virus completely, they’ll suppress it by a significant amount. So they don’t get as sick. “The question then becomes, are those viruses that are still able to replicate in people who are immune, is there enough virus to continue to be transmitted as it is now? “And I think the answer is no, because there’s less virus in those people ... so there’ll be much more limited transmission. That much we know already. “The question then becomes, in the context of widespread vaccination, how much more prevalent will this virus be? How quickly will it continue to change in this context of a much less susceptible population? I’m going to say I think the outlook is good, assuming high enough numbers of people are immunised. “It’s not just a case of vaccinating our own country, we need to see the whole world vaccinated,” she added. “What is the point at which people who’ve been fully vaccinated will be allowed to travel to countries which either have higher rates of vaccination or lower rates? That has to happen at some point. “How do you manage that when they come back in the country? And at some point, there’s going to be a question about people who are not vaccinated, who want to leave the country. That’s going to be interesting.” Professor Turville said boosters and reformulation of the vaccines would be needed for some of the variants that will come along. “I kind of see it as almost like painting the Harbour Bridge, right? You start vaccinating the whole population. And then you have to think about boosting it,” he said. “We haven’t quite got our head around how long the vaccines are going to last, how the variants are going to impact the length of that vaccine coverage. Does that mean we’re going to need a booster in six months? “All of these questions we still don’t know, because we’re only 14-15 months into this.” The experts agree the choice facing unvaccinated Australians is whether to become susceptible hosts for the virus — and in doing so help it mutate — or join the global effort to starve it to death, or at the very least render it harmless.