Behind a building in Melbourne’s northern suburbs is a long, narrow room roughly the size of a tennis court.
Technicians and operators – fully dressed in protective clothing, gloves, goggles, hairpins and masks – are busy walking around, handling a variety of shiny stainless steel tools that look like kilometers of plastic tubes.
There are people here all the time too – it’s a 24/7 operation.
That’s because this room, part of CSL’s Broadmeadows factory, is where 50 million doses of the Oxford-AstraZeneca COVID-19 vaccine will be planted.
Earlier this week, that vaccine approved by the Gene Technology Regulatory Office. Currently being reviewed in the Therapeutics Good Administration.
And as millions of Australians roll up their sleeves for the vaccine, the injection itself may only take a few seconds, but it will take three months to manufacture.
Host with the most
The AstraZeneca vaccine is known as a biological vaccine. This requires the help of living organisms to be produced.
Many medicines are produced this way, including vaccines. The HPV vaccine, for example, which protects against cervical cancer, is one of them.
AstraZeneca’s COVID-19 vaccine relies on a type of cell called HEK 293.These cells were originally extracted from the kidneys of human embryos – hence HEK – in the 1970s. They grow well in the laboratory and are a component commonly used in medicine.
HEK cells don’t actually end up in vaccines. Instead, they developed an important part of the vaccine – the adenovirus, which carries the DNA spike protein blueprint.
So the first step in making the AstraZeneca vaccine is growing an army of HEK cells.
Just as you might get a sourdough starter from a friend, AstraZeneca, in November, supplied the CSL with tiny frozen tubes, each containing only milliliters of HEK cells.
CSL’s job is to take these bits and pieces and multiply them to fill the tiny water tank.
And it’s not a simple matter of putting cells in a big tub, adding nutritional broth and other substances, and letting them grow.
HEK’s cells prefer company. They reproduce faster if they are busy with other people.
So the cells are started in a 10ml glass bottle. After they fill them, they are transferred to a slightly bigger one, maybe 50ml, and so on. (It’s a bit like a hermit crab growing bigger than its shell and finding a bigger one to transport.)
Finally, the cells are transferred into a plastic bag, like a larger version of the blood donation bag, and gently rocked on a mobile platform. The rotating motion helps them grow.
And finally, the now liter HEK cells are poured into the bioreactor: a 2,000 liter stainless steel barrel over 3 meters high.
After a few days, HEK’s cells, which live happily and reproduce in the bioreactor, are ready for the next step.
Introducing the adenovirus
At this point, about three weeks later, the adenovirus enters the process of making a vaccine – literally.
Also supplied in small tubes by AstraZeneca last November, adenovirus was added to awaiting bioreactor and HEK cells.
And while adenovirus is engineered so that it cannot replicate in human cells – it is missing the important genes that make it possible – HEK cells have been altered to encourage adenovirus to infect and replicate within them.
Over the next six days, adenovirus infected HEK cells, multiplied, and continued to infect more HEK cells.
HEK infected cells are sure to die. But after them, the number of adenoviruses increased dramatically.
Next, it’s time to filter and purify the adenovirus from the pale pink bioreactor broth.
This is done using a technique called capture chromatography.
The liquid drips through a membrane designed in such a way that the adenovirus sticks to it, but everything else flows right away.
The different fluid is then sent across the membrane, changing its charge so that it releases its grip on the adenovirus, which then collects.
The bulk concentrated adenovirus vaccine is frozen at -65 degrees Celsius in a 20 liter cryovault plastic container.
And their job is now done, HEK’s remaining cells are destroyed.
Fill and finish (and test)
The first part – growing, harvesting and freezing – lasts for about six weeks on CSL’s Broadmeadows website.
The next six weeks involve diluting the vaccine to the correct concentration, packaging it up, tons of testing and preparing it for shipment to the clinic for use. This is called “fill and finish” and will take place at the Parkville facility, 14 km south of Broadmeadows, starting next week.
And while it sounds straightforward, it’s easier said than done.
Adenovirus vaccine can only last a long time if it is not refrigerated. So from the moment the block of vaccine ice is removed from deep freeze, the clock is ticking.
First, the cryovault blocks are thawed – again, on a rocking platform – at room temperature. This takes more than a day.
The liquid concentrate is then mixed with a buffer solution to produce about 200 liters, tested for concentration (which takes several hours) and then adjusted to levels set by AstraZeneca.
Why not inject adenovirus directly? Buffer solutions do a number of things, such as stabilizing the vaccine and maintaining its pH.
After the vaccines are mixed, they pass through two pharmaceutical filters to ensure that they are completely free of bacteria or other viruses.
The sterile liquid is eventually taken to the filling section, where 6.5ml – that is, 10 doses – are placed in a sterile glass bottle and covered with an aluminum liner and rubber stopper.
(The air above the filling machine is classified as “Grade A” air – the cleanest pharmaceutical grade air as defined by global regulations.)
It takes about 12 hours to put 200 liters into the bottle, and each batch ends up providing about 300,000 doses.
But that’s not the end of the process – not too far.
Then there are nearly two weeks of inspections and at least 14 tests – not including those conducted by the Therapeutic Goods Administration at the Canberra lab – and a final documentation check by AstraZeneca.
AstraZeneca, at last, gave the final green light to release a vaccine.
And then, after 12 weeks, it’s ready to go.
Safety and specifications
The entire vaccine process is carried out according to the strict specifications set by AstraZeneca.
Batches are tested at all stages, from raw materials, such as the chemicals used to grow HEK cells and the pouches they live in, and to contamination and purity.
Even quality control testers, who inspect each bottle after it is filled, undergo rigorous training beforehand. They were given a row of bottles to examine. Some have hidden defects.
They must find all defects three times to qualify.
And not all bottles are expected to make it through the mail. Between 2 and 5 percent may be rejected, based on the previous vaccine manufacturing process.
Even though the production line is up and running in a few months – a process that usually takes the best time of a year and a half – these are still early days for CSL. The first few batches did not produce as many adenoviruses as expected.
But that’s the very nature of using living organisms, such as HEK cells, to make things. You just don’t know how they’ll act every time.
However, the production line at Broadmeadows continues. Multiple batches at various stages in the pipeline keep the product growing.
And once the first batch of vaccine is released, the company hopes to get more than a million doses out each week – with the potential to double that down the road.