Covid reinfections rise

Figures from across the country show there are now tens of thousands of Australians who have had COVID more than once, with “COVID reinfection” generally defined as a second encounter with the virus at least three months after the first infection.

In Victoria, more than 20,000 reinfections have been recorded. It is detecting reinfections through data-matching processes.

In New South Wales, that figure is more than 11,300 and nearly half of those occurred after the Omicron variant emerged there last November.

In South Australia, there have been more than 1,700 reinfections, and in the Northern Territory, there have been more than 220. 

The ACT has recorded more than 670 reinfections — and 70 per cent of those had both infections since the arrival of Omicron.

There have been 112 in Western Australia, which was the last state to re-open to Australia and the world. 

Tasmania has only just begun tracking reinfections and does not have valid data yet.

Queensland does not collect information on reinfection.

For some people, those symptoms can continue long-term. Not a lot is known about long-COVID but researchers are trying to change that. 

According to the Australian Bureau of Statistics (ABS), there are now 47 Australians who have lost their lives to long-COVID. For them, the infection led to serious and lasting complications — often lung diseases such as chronic pneumonia. 

Virus has ‘tricks up its sleeve’

Some countries, such as Denmark, have scrapped testing requirements, while others have been testing far less, meaning fewer COVID-19 infections are being recorded. However, for many countries still recording data, reinfections are on the rise.

Alex Sigal, a virologist from the Africa Health Research Institute in Durban, was one of the researchers who first identified the Omicron variant. 

“Omicron is very good at getting through pre-existing immunity,” he said. “In South Africa, we are at the tail end of a wave with Omicron sublineages BA.4 and BA.5, which were reinfecting a lot of people who were previously infected with the original [strain].”

Both sublineages are also present in Australia. The good news, he said, was that the disease seems to be milder for most. 

Professor Sigal recently researched samples from patients previously infected with the original Omicron strain. While the sample size is small and the study is yet to be peer reviewed, it found the antibodies from the original Omicron BA.1 infection were not very good at dealing with the subvariants BA.4 and BA.5.

“These two sublineages evolved some mutations that enable them to escape from the original Omicron immunity,” Professor Sigal said. He said there was good immunity in the population because of vaccines and breakthrough infections, and he was encouraged by the fact most people infected made a full recovery and experienced milder disease. He said vaccines are working well to keep people from getting severely sick.

But he did have one major worry. “We are giving the virus a chance to explore all possible avenues of evolution,” he said. “It has tricks up its sleeve.”

Omicron ‘continues to surprise’

In Sydney, researcher Stuart Turville, a virologist from the Kirby Institute at the University of New South Wales and his team are learning more about immunity, particularly for those most at risk from the virus.

He said the antibodies appeared to be in decline much sooner in people who only experienced a mild illness. “[You’d think] ‘well, that’s a good thing’,” Dr Turville said. 

“But [what’s] left in terms of the antibodies? There is not a lot there and they are going to wane over time.” Like Professor Sigal, he believed nothing in this pandemic could be assumed or taken for granted.

“Omicron is doing very different things,” he said. “It has changed the way it gets into our body and enters cells [and] it continues to surprise us.

“This thing changes so fast, in the next six months we may not be talking about Omicron, we may be talking about the next letter in the Greek alphabet.”