Three years after the mysterious MERS virus first emerged in humans, and as South Korea reports its 19th death in the current outbreak, scientists and drugmakers say there is no excuse for not having a vaccine that could have protected those now falling sick and dying.
South Korea's health ministry reported four new cases of Middle East Respiratory Syndrome (MERS) on Tuesday, bringing the total to 154 in an outbreak that is the largest outside Saudi Arabia. The ministry also said three patients infected with the MERS virus had died, taking the death toll to 19 in an outbreak that began in May.
The facts behind the coronavirus that causes MERS have been slow to emerge, partly due to a secretive response in Saudi Arabia, which has suffered an outbreak stretching back to 2012.
But scientists do know that it is similar to the deadly SARS virus, that it probably originated in bats, that it is linked to camels, and can pass from person to person. They also understand its molecular structure.
That all yields scientific detail for researchers to begin developing a vaccine, and there is clear frustration that work on one has barely begun.
The problem is that big pharmaceutical firms are uncertain about the economics of such a vaccine and no governments have yet offered to underwrite a major research effort.
"The question is: How long are we going to wait around and just follow these outbreaks before we get serious about making vaccines?" said Adrian Hill, a professor and director at the Jenner Institute at Britain's Oxford University.
"There is no sign of MERS going away. It's been around since 2012. And there is really clear evidence now of human-to-human transmission."
The vast majority of MERS infections and deaths have been in Saudi Arabia, where more than 1,000 people have been infected since 2012, and some 454 have died.
Yet cases of the disease have already been recorded in at least 25 countries, including the United States, China and Britain. MERS, which causes coughing, fever and breathing problems, can lead to pneumonia and kidney failure.
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Some scientists suspect it has probably crossed other international boundaries undetected, since diagnosing MERS and distinguishing it from other respiratory illnesses that kill elderly or sick people in hospital may not always be possible.
MERS infection is caused by a coronavirus from the same family as the one behind Severe Acute Respiratory Syndrome (SARS), which killed around 800 people worldwide in 2002-2003.
High death rate
MERS has a much higher death rate - 38 percent versus around 10 percent for SARS, according to World Health Organisation figures - but it also spreads more slowly from person to person, making it less of a threat, for now.
"The chances are that South Korea will control it," said Hill. "But should we be taking this risk? No. Should we have made a MERS vaccine? Yes. Could anyone have afforded it? Yes, the government of Saudi Arabia. So should something be done? Yes, someone should go and develop a MERS vaccine sooner rather than later."
So far only a handful of small biotechs, including Greffex, Inovio, Novavax, have done any MERS vaccine work and their research is still pre-clinical.
Larger drugmakers, however, such as GlaxoSmithKline, are keeping an eye on the situation.
"We don't have an active MERS program but we are certainly thinking about what we should do if this becomes an issue," said Ripley Ballou, an infectious diseases expert at GSK who has led the company's Ebola vaccine work.
"There is a threat list of diseases that people think are potentially going to do something and MERS is at the top."
For profit-orientated drug companies, the problem is working out who is going to use a vaccine, who is going to pay for it and whether this is a commercial market.
Many experts, including billionaire philanthropist and champion of global health Bill Gates, now argue there should be a much more structured process whereby governments and companies work together to back early vaccine development work.
It is not as if we don't have the scientific know-how.
"Viruses are pretty simple organisms and they all have antigens on their surface that are necessary to get them inside cells," said Ballou.
"Everybody knows what the target for MERS is, it is the core spike protein, which is one of things that targets the cell receptor and allows it to get in. It's a single protein that can be used to induce an immune response."