We are very likely to develop immunity to COVID-19, making re-infection unlikely and raising the chances of vaccines being highly effective, according to the Australian scientist who discovered an important way the immune system fights viruses.

Key points: Professor Doherty does not think contracting COVID-19 twice is very likely

Professor Doherty does not think contracting COVID-19 twice is very likely He says if a patient did catch it twice, the prior infection would give them rapid immunity

He says if a patient did catch it twice, the prior infection would give them rapid immunity He believes a vaccine will be available within 12 to 18 months

In 1996, Peter Doherty won the Nobel Prize in Physiology or Medicine for discovering how the immune system identifies cells that have been infected by a virus.

He said reports of people contracting COVID-19 twice were unlikely to be true.

"I would be sceptical. But you can't say with absolute certainty," he told the ABC.

"I would think even if it was a reinfection, that your prior infection would give you very rapid immunity and you would recover very quickly."

Professor Doherty said it was more likely the test results suggesting the patients were clear of the virus were wrong.

That could happen if the virus was not infecting the part of the body where the swab was taken from but instead infecting deeper in the lungs, Professor Doherty said.

"I suspect they've been infected all along. It's just that this area that's been sampled hasn't been detecting it," he said.

"My guess would be we'd have pretty solid long-term immunity, quite frankly."

He said with some flu strains, people who had been infected had strong immunity 50 years later, but not much work had been done on coronaviruses until SARS — another coronavirus — was identified in 2003.

The coronavirus causing COVID-19 was not a particularly rapidly-mutating one, he said, giving more hope that immunity — or a vaccine — would provide long-term protection.

Australian researcher and Nobel Prize winner Peter Doherty. ( Supplied: Department of the Prime Minister and Cabinet )

He said estimates a vaccine would be available within 12 to 18 months were very realistic.

"I think the 18 months is probably on the long side," he said.

"It may well be that China may bash ahead a lot quicker, then come up with an effective vaccine.

"I hope we'll have something in 12 months.

"I would say it's very likely we will develop a vaccine for COVID-19 and it will be a good vaccine."

Quieting the immune system in severe cases

Professor Doherty said there was also hope for treatment of severe cases of COVID-19, by quieting part of the immune system's response to the virus.

"Some of the symptoms that we see in a virus infection are not due to the virus causing damage, they're the response we make to it," he said.

Professor Doherty won his Nobel Prize for discovering how the immune system identifies cells that have been infected by a virus. ( ABC News: Supplied )

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In some of the most severe cases, it appeared the immune system was going into overdrive and an inflammatory response to the virus was killing people, he said.

He said existing drugs used for inflammatory conditions like rheumatoid arthritis had some promise in treating that, by blocking the inflammatory molecules produced by the immune system.

"I believe there are some promising results out of China, where they are blocking some of those molecules," he said.

Professor Doherty hopes a vaccine will be ready within a year. ( ABC News: Ron Ekkel )

How to protect yourself

Professor Doherty warned people to take this virus very seriously.

"Do not think that this is just another influenza. It's killing at least 10 times as many people as influenza," he said.

"And it's particularly lethal for those in their 70s and 80s. It is dangerous and older people need to isolate themselves."

And he had one other piece of advice.

"If you're a smoker, do try to stop," he said.

Recovering from COVID-19

Australian researchers have found the body is capable of fighting off COVID-19 and in mild to moderate cases, the body's response to the virus is similar to its response to influenza.

The Centres for Disease Control in the United States has said it was not yet known for how long, or if at all, a person who had recovered from COVID-19 was protected from developing the condition again.

NSW Health indicates that for someone with an ongoing health issue or respiratory condition, it may take weeks to recover.