The maker of one of the COVID-19 vaccines that Australia is relying on to reopen the nation to international travel now expects to ship only half the vaccines it originally promised to deliver, as a result of supply chain problems.

Pfizer Inc now expects to ship 50 million vaccines, not the touted 100 million it promised, according to The Wall Street Journal.

Australia had ordered around 10 per cent of those touted vaccines – 10 million doses – to rollout in Australia.

That’s enough to vaccinate 5 million Australians with the two-shot vaccine. But there’s serious question marks now over whether that can be delivered.

“Scaling up the raw material supply chain took longer than expected,” a company spokeswoman told the WSJ.

“And it’s important to highlight that the outcome of the clinical trial was somewhat later than the initial projection.”

It’s not the main vaccine Australia is relying on however, according to Health Minister Greg Hunt who noted we have contracts in place for four different vaccines.

Mr Hunt told news.com.au that Pfizer had reaffirmed the planned order as recently as this week and Australia had planned ahead with a multi vaccine strategy to cover all contingencies.

“We’re very fortunate that we’ve been able to select and then acquire, which is the second stage – four vaccines … the AstraZeneca vaccine for 33.8 million units, the Pfizer vaccine for 10 million units, the Novavax vaccine, 40 million units, and Australia’s own CSL – University of Queensland vaccine for 51 million units, as well as 25.5 million units of access through what’s known as the COVAX International Facility,’’ he said on Thursday.

“We’re moving quickly but safely, and we’re making sure there are no compromises because the safety of Australians is the number one priority.”

Mr Hunt has outlined a timetable to commence the rollout of the vaccine in Australia by March.

“We are on track for decisions on the early vaccines by the end of January. We are on track for first vaccinations, beginning with our health workers and our aged care residents subject to approvals, in March,’’ he said.

Pfizer’s woes are a far bigger problem for the UK that ordered 40 million Pfizer doses, enough to vaccinate 20 million people.

The expectation now is that only four to five million vaccines will be shipped.

Prime Minister Scott Morrison confirmed on Thursday that arrangements have been put in place to secure access to four vaccines, “all of which, all of which are proving to be very promising but still have stages to pass in the months ahead”.

But with the COVID-19 outbreak “stable” in Australia, he suggested that time was on the government’s side rather than rushing the rollout of the vaccine before safety checks were complete.

“You’ll be aware of the decisions that have been taken in the United Kingdom no doubt, the UK will need to deal with their situation and their circumstances in their way. Of course they should,’’ he said.

“In Australia we are in a very strong position and that enables us to get this right, to get the balance right, to ensure first and foremost the safety, which enables us to then roll out the vaccine successfully across the country.”

The Health Department’s vaccine expert Professor John Skerritt said Australia had provided three vaccines with what’s known as provisional designation.

“Two of them are amongst the four vaccines that the government has procured, the AstraZeneca vaccine, the Pfizer vaccine,’’ he said.

“It’s not a full regulatory approval. We will – when the final data is in – for safety and efficacy, and I’m hoping that will be in the coming weeks, but we are at the mercy of the companies, work(ing) through the summer period. Unfortunately, my staff have been told to put away their swimsuits and towels and to work as quickly as we can …

“We are still hopeful, but if we receive a full submission in the next week or two, that late January, beginning of February, well ahead of the March date the government has mentioned that we will be in a position to approve one or more.”

Australians who are severely overweight and ‘guinea pig’ politicians will get to jump the queue for the new COVID vaccine.

But children are likely to be last in line for the jab, which will not be linked to the nation’s No Jab, No Play laws that can strip welfare payments

The guidelines agreed to for the rollout of the vaccine will see seniors in nursing homes and their carers and older Australians vaccinated first.

But the preliminary advice on general principles to guide the prioritisation of target populations in a COVID-19 vaccination program in Australia notes that obese people should get the jab first.

“These at-risk medical conditions include, but are not limited to, immunocompromised, multiple comorbidities, chronic lung disease, diabetes, cardiovascular disease and severe obesity,’’ the advice states.

The Health Minister said children were likely to be left to last until the safety of the vaccine for children was confirmed.

“The second thing is that they will consider the position with regards to children, and vaccinations, but at this stage it has been indicated that it is unlikely that children should be at the front of the process,’’ Mr Hunt said.

“There have not been many global tests in relation to children and safety becomes a paramount concern.

“Finally, we have said previously that it is going to be voluntary, and at this stage there were no plans to impose or draw upon other programs such as the no jab no pay.”

Any record of vaccinations will be up to the patient to share with airlines or employers.

The Morrison Government has outlined a staged process to roll out the vaccine in Australia, suggesting it won’t be rushing to match the UK’s announcement.

“We have got to get that balance right and we will implement the vaccine here in Australia according to Australian needs and Australian conditions and the challenges and opportunities we have here,’’ the Prime Minister said.

“As we move into the vaccine., our first priority is that it be safe. It must be safe for Australians and that is what they would expect of us. The UK will need to deal with their situation and their circumstances in their way.”

Therapeutic Goods Administration chief Professor John Skerritt said there were “hundreds” of vaccines under development and at least a dozen in the late stages of readiness to rollout.

“I’ve been asked which of the three horses are leading the race but it changes by the day and it often depends on the progress and completion of clinical trials run globally,’’ he said.

“Let’s say for example the vaccine is better tolerated in pregnant women. We’ll have that option because we have invested in a range of vaccines,’’ he said.