The vaccine rollout that “wasn’t a race” is now speeding up and immunising younger people will become key to shielding the community from fresh outbreaks as more doses of the Pfizer vaccine land on our shores. But we are still months away from the new thresholds set by the federal government for reopening Australia.

Until 70 per cent of people aged 16 and older are fully vaccinated, short, sharp lockdowns will be standard for stamping out the highly infectious Delta variant now surging around the world. The modelling by the Doherty Institute underpinning national cabinet’s four-stage plan to eventually open borders and “live with the virus” shows that going hard early to crush COVID through lockdowns not only drives down infection rates but, on an analysis by Treasury, minimises the economic pain of a looser, longer lockdown. As vaccination coverage ticks up, that cost will plummet even further, and exemptions for the immunised will offer new freedoms until restrictions are no longer needed.

But how did government arrive at those targets? What’s happening with the Pfizer supply? And when do experts think life might actually go back to normal?

Remind me again how the vaccine rollout is going?

Since it kicked off in late February, the national rollout has lagged months behind schedule. In aged care homes, for example, it was originally expected to take just six weeks, but, while most residents have now been fully immunised, only half of aged care workers and disability support staff have had at least one dose.

Right now the main problem is supply. When vaccines first hit the market, Australia was among a clutch of wealthy nations ordering many times over what they needed to vaccinate their populations. But in those early orders Australia relied mostly on the Oxford vaccine, AstraZeneca, which can be made onshore by local manufacturer CSL, as well as the molecular clamp vaccine developed by the University of Queensland. The UQ vaccine didn’t make it through trials. And while, AstraZeneca has proven highly effective, used widely around the world, and in enough supply to cover our population, it’s also been linked to rare cases of blood clotting.

That risk, though tiny, is a little higher in younger age groups, who also have a lower chance of dying from COVID itself. So, like in the UK, Australia’s government’s expert advisory group ATAGI recommended the mRNA vaccine Pfizer as the preferred vaccine for young people (in Australia’s case under 60-year-olds). Pfizer has only been available to 40 to 59-year-olds until very recently due to limited supply.

As Sydney battles its worst outbreak since the pandemic began, that AstraZeneca advice has changed again: people over 18 in outbreak areas should consider getting whatever approved vaccine is available (given the risks from COVID, including clotting, are still much higher). Many young Australians across the country have since consulted their doctor to get AstraZeneca even as figures show some older Australians appear to still be waiting for Pfizer.

Now, after weeks of outbreaks, lockdowns (and bigger deliveries of Pfizer), the pace of vaccinations is accelerating. By the end of July, more than 100,000 doses were being given out every day, on average. (It took 45 days to deliver Australia’s first million doses but just six days to move the total from 11 million to 12 million, as it stood on August 2). If we keep up this rate, experts expect we will hit our target out of the current “suppression” phase of the road map (70 per cent of those 16 and over vaccinated with two doses) by late November, and 80 per cent to move into the “consolidation” phase (where borders start to reopen in earnest) by Christmas (see graph above).

So young people are being vaccinated?

Until now, Australia was vaccinating those most at risk of dying from COVID – older people and those with underlying medical conditions first, as well as some frontline workers. “That was the right thing to do,” says Jodie McVernon, who has been leading the modelling work at Doherty. “But now the strategy has changed.”

Their model shows bringing forward vaccinations for 16-39-year-olds, the cohort most active in the community and so most likely to spread the virus around, will start to cut the transmission of COVID, not just its severity in patients. That in turn offers the best vaccine coverage for everyone in the community, from older generations down to children not covered by immunisation right now.

On current supply constraints, which were also plugged into the model, 30-39-year-olds will now become eligible for a Pfizer vaccine across Australia around the end of the month, early September, says Lieutenant General John Frewen, who is co-ordinating the rollout under Operation COVID Shield. And 16-29-year-olds should follow in October. That coincides with when a large chunk of the 40 million Pfizer doses Australia has ordered for this year will have landed (see below).

UPDATE: On August 19, national cabinet agreed that vaccine eligibility would expand nation-wide to people aged 16-39 on August 30, rather than starting with 30-39-year-olds.

What’s behind the 70 and 80 per cent targets?

Australia, having kept COVID cases low compared to most of the world, is now relying on vaccines to get to “herd immunity”. That’s when enough of a population is protected that the virus starts to slow and die out. For COVID, scientists put it somewhere between 70 and 90 per cent. But McVernon says there’s no such magic number for vaccine coverage. Both Pfizer and AstraZeneca give good protection against catching COVID, particularly a severe case, and roughly halve the chance of spreading it on. Yet no vaccine is perfect; some cases will still break through.

When Delta emerged in late 2020, twice as infectious as the original virus that came out of Wuhan the year before, the government had the Doherty Institute model adult vaccination coverage rates of between 50 and 80 per cent. At 50 to 60 per cent of adults immunised, McVernon says, they found outbreaks were still very hard to control, considering how fast Delta has been moving through the Australian community. Baseline public health measures such as hand hygiene, social distancing, masks and contact tracing only brought the infection rate back down to that of the original Wuhan virus, meaning lockdowns were still required.

But as coverage reached 70 to 80 per cent, the need for tough measures like “the Victorian stage four lockdown” fell, and the more standard public health response was enough to “turn what might otherwise be a bushfire into more of a controlled backburn”.

Are the targets high enough to reopen?

Stephen Duckett, a former federal health department secretary now at the Grattan Institute, is quick to point out that those 70 and 80 per cent vaccination targets since agreed by national cabinet leave out children, and so actually represent about 56 per cent of Australia’s total population of 25 million or so. “Children still spread the virus,” he says. “We still think you should get to 80 per cent of the entire population vaccinated before you throw out lockdowns and open borders.”

Burnet Institute epidemiologist Mike Toole, who has previously run outbreak vaccination campaigns in the developing world for the US Centers for Disease Control and Prevention (CDC), agrees. “Under 60 per cent total leaves too much room for the virus to spread.”

But other experts have backed the government’s adoption of the Doherty modelling. Deakin University epidemiologist Catherine Bennett says the thresholds for moving away from lockdowns and reopening borders are actually fairly conservative but notes the game-changing Delta strain will continue to dictate how Australia manages the pandemic.

Tony Blakeley at the University of Melbourne thinks Australia is on track to meet and perhaps exceed the road map’s targets, even if lockdowns linger as a possibility until its fourth and final “post-vaccination” stage (which does not have a target as yet). If we don’t hit the first two targets by December, his university’s own modelling suggests we could still move through to the next phases with some updated caveats, such as keeping borders closed to high-risk countries.

Virologist and advisor to the World Health Organisation Gary Grohmann says Australia generally shoots for very high vaccination rates when it comes to infectious disease, at least 85 per cent of the total population. “Flu is lower, but for things like polio, hepatitis, measles, we don’t even think about them anymore.”

That’s outside a pandemic of course. Some medical experts such as Brendan Crabb of Burnet and Nancy Baxter of the University of Melbourne have suggested Australia shouldn’t be aiming to “live with this virus” the way we do flu, as the Prime Minister has proposed. That could downplay the risks of COVID. Crabb says Australia, with its comparatively low caseloads, may even be in a unique opportunity to approach COVID more like the highly infectious measles, with less tolerance for significant transmission in the community and so vaccination targets as high as 95 per cent.

Duckett understands their concern but says “the point of a vaccine is that they do bring the risk down to something like flu, because the hospitalisation rates plummet even if you get cases”. At the 80 per cent adult coverage modelled by Doherty, hospitalisation and infection are about on par with seasonal flu levels.

OK, but when is all the Pfizer coming? And the Moderna?

On August 2, 5.6 million of the 12.3 million or so vaccine doses already given in Australia were Pfizer. And almost 8 million doses of the 40 million we’ve ordered for this year had been received. Exact supply numbers are usually only locked in four weeks in advance, when Pfizer confirms the final numbers being released that month. But General Frewen says Australia is working to bring the rest of those 32 million doses forward to more than 1 million arriving each week. According to his roll-out plan, we will have 5 million Pfizer doses to use in August, 4 million in September, 10 million in November and 6 million come December. In the meantime, ATAGI has already recommended spacing out the interval between first and second Pfizer doses from three weeks to six in order to speed up first inoculations.

From September, the first of the 25 million Moderna doses on order will also begin arriving – 10 million is expected by December. Moderna, another mRNA vaccine like Pfizer already used widely overseas, still needs to clear Australia’s regulator the Therapeutic Goods Administration, as does the protein vaccine Novavax which has so far not been used elsewhere but has very promising clinical trial data. Novavax is now not expected until next year in Australia, as are a further 60 million Pfizer doses to be used as boosters, and then another 25 million Pfizer boosters in 2023.

While AstraZeneca is being slowly phased out of the rollout as the focus switches to younger cohorts, General Frewen says “we have enough for anyone that wants it, we can get it to any pharmacy that needs it usually within 24-48 hours, and we’re sending some to the Pacific too ... where the need is urgent at the moment”. He’s confident there’s now enough supply coming online to get everyone at least a first dose by Christmas.

UPDATE: On August 15, the federal government announced a further 1 million Pfizer doses would be coming from Poland, with more than half earmarked for Sydney outbreak hotspots.

Shouldn’t we vaccinate young people right away?

McVernon says opening doses up to 30-39-years-olds first and then the 16-29-year-old cohort makes sense to maximise take-up in each group, without overwhelming the system. “When you open up to a new group, everybody runs in ... and then demand starts to wane a little bit. [As for which order] it’s really a moot point, as long as you can get high coverage in both of those groups ... those are our peak spreaders. They will bring COVID home to their children, they will take it home to their own parents.”

Some jurisdictions such as the ACT, Tasmania and WA have already brought forward 30-39 year olds in their vaccine allocations in recent days, and NSW has been working to open Pfizer up to everyone over 18 next. Frewen says that’s logical and the Commonwealth is helping NSW vaccinate essential workers in south-west Sydney, where the Delta outbreak is raging. They are starting with staff in supermarkets and food distribution centres.

Toole and infectious disease physician at the Kirby Institute Greg Dore say that bringing forward younger, more mobile cohorts, who often work in these kinds of public-facing service jobs, is crucial in an outbreak zone. Duckett thinks NSW could go one step further: “I’d be vaccinating absolutely everyone I could in Fairfield [in Sydney’s south-west].”

Year 12s in those hotspots are now getting Pfizer shots this month ahead of exams. As for vaccinating children under 16, the TGA has already approved Pfizer in 12-15-year-olds nationally, so children in that age group with underlying health conditions such as severe asthma as well as Indigenous kids can already get vaccinated. General Frewen says work is under way to vaccinate 12-15-year-olds more widely through schools later in the year, depending on the medical advice that comes out of ATAGI.

While some experts have pointed to schoolyard Delta outbreaks in otherwise highly vaccinated populations such as Israel, McVernon says the data shows that, unlike with the flu, kids have a much lower chance of catching and spreading COVID. “Obviously maintaining their education and protecting them is still important,” she says. But vaccinating children will not significantly bring down community spread of the virus.

But we’re not done with lockdowns? When can we actually reopen?

The new road map is significant too for signalling states will use short, sharp lockdowns against Delta until vaccination coverage significantly picks up. As recently as late June, the Prime Minister was praising NSW for “resisting going into a full lockdown”, having previously criticised some of Victoria’s lockdowns. Now the government says they are the most cost-effective way to manage outbreaks right now, though all lockdowns are punishing on people. “We knew snap lockdowns worked long before this modelling came out,” Toole says. “But it’s too late for NSW. I wish they’d changed their tune six weeks ago.”

That modelling did have one notable caveat: Australia could only move away safely from lockdowns at 70 per cent adult vaccination coverage if other testing, tracing, and quarantine measures stay at the optimal levels seen in NSW during the Christmas and new year outbreaks. If cases start to overwhelm the health system again, then, similar to Melbourne’s second wave last winter, those strict level-four lockdowns will still be called for about 22 per cent of the time.

It might be that lockdowns are needed earlier than ever to stop freight-train Delta, Bennett says. On Thursday, Victoria gave just hours notice for its seven-day snap lockdown, 8pm rather than the usual midnight start. Premier Daniel Andrews has said that’s because, during the state’s last outbreak, there was still transmission happening on the eve of the lockdown.

Bennett notes that a big lag in vaccinations in one or two states could hold back the national rate. But she’s hoping “healthy competition between states will prevail”.

Even coverage is also crucial along socio-economic lines, McVernon says, to make sure vulnerable communities are not left behind. Already in the rollout, the wealthiest parts of NSW and Victoria, for example, have the highest rates of vaccination while rates are low in the heart of Sydney’s Delta outbreak in its poorer west and south.

Epidemiologist Mary-Louise McLaws, who also advises the WHO on COVID, says the government was warned early on it would need a plan to reach people in low socio-economic and culturally diverse communities, who may not have their own GP, understand the already confused vaccine messaging or be able to take time off work for appointments. General Frewen says widening the rollout to those falling through the cracks will now be a priority as it speeds up, citing recent work with religious and community groups in NSW.

Incentives will also be considered when demand starts to hit the wall of vaccine hesitancy. “But we’ll probably get to 80 per cent before then,” Duckett says. “Right now the problem is supply.” General Frewen expects that planned exemptions from measures such as travel bans, quarantine and lockdowns for those vaccinated will resonate with people more than cash incentives (or some of the wackier lotteries and cow giveaways overseas).

Blakely and Dore, meanwhile, see potential to reopen what they call low-risk avenues in and out of the country sooner than planned if all goes well. Blakely has suggested allowing capped international student arrivals from countries with low infection rates, such as China, before we reach 70 per cent, while Dore says allowing fully-vaccinated Australians to leave the country, say to see relatives, would bring virtually no risk. “Especially if we say the trip must be more than six months by which time the community is at 80 per cent coverage,” he says. “Or we could start letting fully-vaccinated people come in through home quarantine rather than the hotels.”

Still, Toole, Duckett and Grohmann stress that quarantine will need to remain an important part of Australia’s COVID defence for some time, questioning the delay so far in building open-air quarantine facilities close to airports.

Grohmann expects some baseline restrictions will remain, like water restrictions, for the foreseeable future, even as booster shots help guard against new variants. “Whether that’s using QR codes, some density rules ... We don’t leave taps running, even when our dams are full. We need something for COVID too.”