Religious leaders have raised ethical doubts over one of Australia's primary coronavirus vaccine hopes because scientists have used foetal cells in its development.

Developers at Oxford University and pharmaceutical firm AstraZeneca are using cell lines from an electively aborted foetus in the vaccine candidate, with Anglican, Catholic and Greek Orthodox leaders questioning the practice.

But using foetal cells in vaccine development isn't new and the Catholic Church has previously expressed qualified support for the use of vaccines derived from these cells under certain circumstances.

We spoke to Bill Lott, a virologist at QUT's Institute of Health and biomedical innovation, to understand the role of foetal cells in vaccine development.

The foetal cells used in vaccine development are derived from a small number of foetuses which were legally terminated decades ago.

The Oxford vaccine uses HEK (human embryonic kidney) 293 cell lines, obtained from a female foetus in the Netherlands in 1973.

"We're using tissues that were from foetuses that were aborted 40, 50, 60 years ago," Dr Lott said.

"It doesn't require newly aborted foetuses."

While living human cells can only divide around 50 times, those foetal cells have been genetically modified so they can divide an infinite number of times.

"That's why we can use the cells that we harvested [decades ago] today," Dr Lott said.

"They're not the actual original cells, they've been immortalised and then propagated over the decades."

This means we'll never need to replace specimens used in development.

"Just by analogy, buying ivory is illegal [because] if you create a market for ivory, then it creates the demand to kill more elephants," Dr Lott said.

"In this case, that's not happening because these foetuses were aborted 60 years ago, 50 years ago, and using these immortalised tissues now is not going to create a need to go and get new ones."

In fact, scientists would prefer to keep using HEK 293 cell lines because they have been repeatedly tried and tested in a laboratory setting and found to be safe.

"When you're making a vaccine you require safety testing," Dr Lott said.

"If we went back and used a different cell type, you're throwing an unknown into the consideration.

"So that will severely slow down your ability to make these things.

"Using HEK 293, we've used it for decades and we know that it's safe."

This week, Australia's Deputy Chief Medical Officer Nick Coatsworth pointed out the use of foetal cells had been a "reality" in past vaccine development.

"The reality for vaccines is that they need cell cultures in order for us to grow them," he said.

"The human cell is a really important part of their development.

"There are strong ethical regulations surrounding the use of any type of human cell, particularly foetal human cells.

"This is a very professional, highly powered research unit at Oxford University.

"I think we can have every faith that the way they have manufactured the vaccine has been against the highest of ethical standards internationally."

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So, how do foetal cells help with vaccine development? Dr Lott explained they operate like a "vaccine factory".

First, scientists need to develop the vaccine candidate and then combine it with an adenovirus vector.

An adenovirus is a particular type of common virus that causes illnesses like bronchitis, pneumonia and a sore throat.

For instance, when you get a cold, you may be infected with an adenovirus, a coronavirus or a rhinovirus.

A vector is an organism that spreads infection by moving pathogens from one host to another.

So an adenovirus vector? "That's an adenovirus that has been sort of emptied out and then you put a different kind of genome in there to make protein," Dr Lott said.

The next step is to put the vaccine/adenovirus vector combination into a big vat of foetal cells.

"The viral vector infects these HEK 293 cells really, really efficiently," Dr Lott said.

"One reason why you use the HEK 293 is because you get essentially 100 per cent infection with the adenoviral vector.

"And what it does is it turns the HEK 293 cells into a vaccine factory."

What do we mean by "vaccine factory"? Dr Lott explains foetal cells begin producing "tons and tons of that modified adenovirus" which they then "spit out into the liquid bit of the cells" called the cell culture media.

"[The foetal cells] start cranking out this massive amount of modified adenovirus, and then you purify those things away from the cell tissue," he said.

"You pull the [cell] media off, and it's just going to be full of the vaccine and essentially no tissue.

"And that's what your vaccine is."

The foetal cells will operate as this "vaccine factory" regardless of whether the vaccine is effective or not so the next step generally involves animal and then human trials of varying scale.

Inherent in the whole process is stripping away the conditioned cell media, where the foetal cells are contained.

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That means a successful vaccine developed using foetal cells will have no remnants of those cells in the final product.

"You purify the vaccine away from the cells that they were grown in, and then you destroy all the cells," Dr Lott said.

"So then you're going to take that liquid and you'll purify it some more, but there are not going to be any [foetal] cells in there.

"There's nothing left when it becomes the vaccine that gets delivered."

Foetal tissue has been used with innovative effect in various strands of medical research.

The difference is some of those processes require fresh foetal cells not the "immortalised" cells vaccine developers can use.

"The vaccine work is pretty straightforward," Dr Lott said.

"But cancer research, the research into the mechanisms of various things cystic fibrosis, haemophilia, rheumatoid arthritis that all required fresh foetal tissue."

Scientists studying Zika virus used foetal cells to discover that the virus crossed the placental membrane and caused brain damage in unborn foetuses.

"[That research] brought out a whole raft of therapies and protections for unborn foetuses [and] "saved a lot of lives, including [the lives of] unborn foetuses," Dr Lott said.

Foetal cell lines have been used in the development of various vaccines, including for chicken pox, Ebola, polio, rubella, shingles, Hepatitis A, and rabies.

Foetal tissue has also facilitated breakthroughs in the treatment of various medical issues including cystic fibrosis, haemophilia, IVF, Parkinson's and Alzheimer's diseases, AIDS, and spinal cord injuries.

Scientists have many different methodologies for developing vaccines and there are a variety of reasons why foetal cells aren't always used.

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"Some of them don't use it because of ethical issues," Dr Lott said.

"Some of them don't use it because they're not using an adenovirus [vector], so they don't really need the HEK 293.

"And there are other [development] strategies.

"There's an mRNA strategy that's very popular.

"So some of them don't require it."

The development of a coronavirus vaccine was time critical because of the virus' devastating public health and economic impacts, Dr Lott said.

Therefore, it was important for scientists to diversify their methodologies in order to develop a vaccine as quickly as possible.

Both stem cells and foetal cells are critical to innovations in medical research but what's the difference between the two?

Dr Lott explains stem cells are basically the earliest iteration of a foetal cell before the cell differentiates itself into, for example, a hair cell, liver cell, eye cell or skin cells.

"A stem cell is simply a cell that can turn into a different cell types," Dr Lott said.

"That first embryonic stem cell can eventually turn into any kind of cell in your body.

"So you've got embryonic stem cells, and then you've got adult stem cells, and in between are the foetal stem cells [which] are partially differentiated.

"So foetal cells contain not only stem cells some of the foetal cells have already differentiated into their final cell type."

In 2005 and again in 2017, the Catholic Church expressed qualified support for the use of foetal-cell-derived vaccines but only if there was no available alternative.

A 2005 "moral reflection" issued by Pope Benedict XVI specifically addressed the issue.

"As regards the diseases against which there are no alternative vaccines which are available and ethically acceptable, it is right to abstain from using these vaccines if it can be done without causing children, and indirectly the population as a whole, to undergo significant risks to their health," the Pope wrote.

"However, if the latter are exposed to considerable dangers to their health, vaccines with moral problems pertaining to them may also be used on a temporary basis.

"We find a proportional reason, in order to accept the use of these vaccines in the presence of the danger of favouring the spread of the pathological agent."

In 2017, the life ethics arm of the Catholic Church issued a statement that: Catholic parents could vaccinate their children with a "clear conscience" that "the use of such vaccines does not signify some sort of cooperation in voluntary abortion".

Earlier this year and in the context of the coronavirus vaccine race, John Di Camillo, an ethicist with the National Catholic Bioethics Center, confirmed: "One is allowed to make use of [vaccine derived from foetal tissue] where there's a serious threat to the health or life of the individual, or of the greater population.

"This does not amount to a strictobligationto use it, but it certainly can be a legitimate choice in conscience if theres that serious reason, and there's no other reasonable alternative."

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Foetal cells are used to make the Oxford coronavirus vaccine. But they came from a foetus in 1973 - ABC News

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