Talking to Professor Michael Toole on the day of his farewell (by Zoom meeting) after 40 years working in infectious disease research and international health at the prestigious Burnet Institute, one gets the sense he could quite happily keep going for another four decades.
He reels off in quick succession some of the countries he has worked or studied in: Thailand, Laos, the United Kingdom, Paua New Guinea, Mozambique, Indonesia, Tibet, the United States, Somalia, Togo, Afghanistan, Myanmar - often in places devastated by war, where he would strive to restore public health systems.
Scientific facts flow from him in a steady stream. While we are ostensibly discussing the reasons why vaccines work so well in fighting COVID-19, the conversation ranges from the eradication of smallpox (Professor Toole met the last person diagnosed with the virus, Ali Maow Maalin) to how toxoid vaccines combat diphtheria and tetanus (they don't attack the germ, rather the toxin created by the germ).
Professor Toole explains how mutations of the COVID virus eliminate the previously existing strain.
"COVID is mutating about once a month; most of those mutations don't go anywhere," he says.
"Some of them become what the World Health Organisation calls 'variants of interest'. So they have the potential to have serious consequences, but then they tend to be out-competed by subsequent variants, like Delta: Delta got rid of Alpha, Beta, and Gamma. And we'll just see what Omicron does competing with Delta; as a percentage of new cases in South Africa, Omicron is approaching 90 per cent Delta is 10 per cent."
The Omicron strain, like the Alpha strain, is missing a gene, which makes it easier to detect, Professor Toole says, with a case in NSW showing this pattern of mutation making it likely the Omicron strain is there.
Professor Toole says the brilliant work of scientists like Katalin Kariko in developing the mRNA vaccine while making sure the human immune response was proportionate is setting the bulwark against future strains of the COVID virus.
"Those vaccines are probably the most valuable because they will be easy to tweak in response to variants," he says.
"You just sort of play with it. There's an immune response against the germ, but not against the rest of the body."
Professor Toole says all four versions of the vaccines, and their sub-versions, will help prevent COVID spreading as it inevitably mutates, by instructing the T (thymus-origin) and B (bone marrow-origin) cells in our body to memorise and attack the COVID pathogen.
"When we're exposed to an infection, we have two responses. One is called an antibody response, and the other is called a cellular response," he says.
"Cellular immunity means that the T cells are primed to instruct these other B cells to make antibodies. And so having both is your best chance at longer term immunity. So we know that current vaccines do induce an antibody response, and we're learning how good they are at producing a cellular response. And Macfarlane Burnet discovered all this."
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