The pace at which scientists around the world have sped toward a coronavirus vaccine has left even experts amazed. Science reporter Jamie Morton asks when New Zealand can expect to see one.
What's happened so far?
Within just months of the pandemic's outbreak, research groups around the world had identified around 100 vaccine candidates.
Now, according to the World Health Organisation's latest landscape report, 29 have reached clinical evaluation - including seven which have reached the crunch stage of phase III.
University of Auckland vaccinologist Associate Professor Helen Petousis-Harris said one of those could even be cleared to begin rolling out by the end of the year.
"I think most people who are experts in this space are fairly confident that we'll have something reasonably soon."
Although scientists haven't had to start from scratch - platforms have already been developed for the Sars and Mers coronaviruses, for instance - the turnaround time has been incredible, given that vaccines typically take a decade to bring to market.
What are the most promising candidates?
Petousis-Harris said three from the field have particular potential.
One was the University of Oxford and AstraZeneca's viral vector vaccine, called ChAdOx1-S, which has already been observed to provoke a T cell response within 14 days of vaccination - and an antibody response within 28 days.
What does that mean?
T-cells are white blood cells that can attack cells infected with the SARS-CoV-2 virus, while antibodies are able to neutralise the virus so that it can't infect cells when initially contracted.
Put together, you have a formidable shield against coronavirus.
Last month, Oxford reported trial participants who received the vaccine had detectable neutralising antibodies.
These responses were strongest after a booster dose, with 100 per cent of participants' blood having neutralising activity against the coronavirus.
Part of the Phase III trial now underway was looking to confirm whether it could effectively protect against SARS-CoV-2 infection.
But already, Oxford researchers say their vaccine hasn't led to any unexpected reactions, and has a similar safety profile to previous vaccines of its type.
Australia was now looking to get its hands on the vaccine, having just signed an agreement to manufacture it.
The other two, also in Phase III, are from a revolutionary new class called RNA vaccines.
While viral vector vaccines use pieces of a pathogen to effectively stimulate an immune response against it, RNA vaccines use smart vehicles, such as nanoparticles, to carry genetic material into a cell, before it codes for specific proteins from a virus.
The LNP-encapsulated mRNA vaccine developed by US' National Institute of Allergy and Infectious Diseases and Massachusetts-based Moderna is specifically designed to induce neutralising antibodies directed at a portion of the coronavirus "spike" protein, which the virus uses to bind to and enter human cells.
Initial, small-scale trials have also found no adverse effects - although more than half of their participants reported fatigue, headache, chills, myalgia or pain at the injection site.
The other candidate - the 3 LNP-mRNAs vaccine created by BioNTech, Fosun Pharma and Pfizer - has shown similarly exciting promise.
Petousis-Harris said the key to an effective vaccine was achieving a safe, lasting and balanced immune response, something those three front-runners appear to be demonstrating.
But each had their pros and cons. While a viral vector vaccine might only require one dose, the RNA candidates took two.
"But these vaccines are relatively cheap and easy to up-scale: to put that into context, you might only need a gram of this stuff to get one million doses."
What about the others?
Petousis-Harris expected New Zealand was less likely to opt for one of the several candidates being developed in China.
But that's not to say they haven't produced some encouraging results, too.
CanSino Biologics' adenovirus type 5 Vector vaccine, for instance, was found in Phase 1 trials to induce a safe immune response.
"Some of the other vaccines at Phase III are what we call inactivated vaccines," she said.
"These are your tried-and-true ones, such as those we used for polio, or use now for influenza ... so we're in more familiar territory."
The downside to these vaccines was the need to grow the virus - which required high-level biosecurity facilities - along with the addition of an immune enhancer to get the right response.
What of Russia's much talked-about Sputnik V vaccine?
While President Vladimir Putin has claimed it's safe and effective, and signed off a mass roll-out in Russia to begin in October, immunologists elsewhere in the world have seriously questioned those claims.
What's New Zealand doing?
The Government has already poured $37m into securing a vaccine for New Zealand, including $5m for manufacturing one here, and $10m for local research.
One Kiwi consortium has been exploring potential home-made candidates - such as an inactivated vaccine approach led by Otago University's Professor Miguel Quiñones-Mateu, and a recombinant spike protein vaccine being developed in Dr Davide Comoletti's Victoria University lab - for the past few months.
Alongside the funding, the Government has put in place a vaccine strategy, aimed at landing enough doses for Kiwis at the earliest possible time.
A big part of that strategy has been building capability for making and distributing a vaccine here if that's needed.
RNZ reported the Government might even offer the vaccine supplier indemnity against any claims arising from its use to help fast-track the process - although regulator MedSafe wouldn't allow a vaccine whose safety wasn't backed by clinical data.
New Zealand is also part of the Covax alliance, which has a goal of delivering two billion doses of safe, effective and approved vaccines by the end of next year.
But it might be that we end up piggy-backing on Australia's deal with AstraZeneca.
Medicines New Zealand Chief Executive Graeme Jarvis said Australian companies were already collaborating with the drug giant.
"There's a company called CSL, they manufacture influenza vaccines for global distribution, but they are also talking to some of the other companies about the potential to manufacture their vaccines as well," he said.
"So it's not unexpected, but we just have to wait and see when the ink dries on the deal."
Australian Prime Minister Scott Morrison said he intended to make the country's vaccine, once available, "as mandatory as you can possibly make it".
In New Zealand, experts have sounded concerns the country might not reach an uptake level ideally needed to be as high as 80 per cent if too many Kiwis are fearful.
Asked today if she intended to take a stance as strong as Morrison, Prime Minister Jacinda Ardern suggested not.
"We haven't done that to date because we've actually been able to get the kind of take-up we need to provide herd immunity ... and I have every expectation we'll be able to do that in New Zealand without needing a mandate."