That brings the company's commitment to Australia to 40 million doses before the end of the year, enough to inoculate 20 million people. It means this country can draw upon a vast reservoir of 170 million doses of the Pfizer, AstraZeneca, and the yet-to-be-approved Novavax vaccines.

The additional Pfizer doses are expected to start arriving around October.

Thursday's news confirmed statements by many experts, including Coalition for Epidemic Preparedness and Covax co-chair Jane Halton, that the decision to withhold the AstraZeneca vaccine from under-50s was a "hiccup and not a roadblock".

The former Finance Department head was speaking in the wake of an after-hours press conference, during which a visibly shaken Prime Minister broke the news that the Australian Technical Advisory Group on Immunisation had advised the government, due to a very low-level risk of blood clotting, that an advisory should be issued recommending the AstraZeneca vaccine not be administered at this time for persons under the age of 50.

The chief medical officer, Professor Paul Kelly, said about four to six clotting events appeared to be occurring for every million doses of AstraZeneca administered.

"It's only been found in the first dose of the AstraZeneca vaccine, usually within four to 10 days after that vaccine," Professor Kelly said.

"But it is serious and it can cause [an] up to 25 per cent death rate when it occurs."

That had led to ATAGI recommending the use of the Pfizer vaccine over the AstraZeneca vaccine in adults aged under 50 who had not already received their first dose of AstraZeneca.

While Pfizer is not without issues of its own, given 11.1 people per million have reportedly suffered an anaphylactic reaction, it is considered safer for the younger cohort in which the risk of clotting is highest.

Australia's decision to go with 50 as the minimum age for AstraZeneca is a cautious one based on the low rates of virus circulating in this country. In the UK, where the virus is actively spreading in the community, the risk of clotting versus the risk of dying from COVID-19 is a different equation, which explains that country's minimum age recommendation of only 30.

While this latest development, in conjunction with well-documented vaccine shortages and delivery and local production delays, has trashed the original timelines, that does not mean the entire vaccination rollout is in tatters.

The Phase 1a and Phase 1b cohorts who are currently being vaccinated are predominantly made up of over-50-year-olds. They include an estimated 190,000 aged and disability care residents, and almost 3 million ambulatory adults aged 70 and above.

The Phase 2a cohort includes almost 6 million people aged between 50 and 69. It will be quite some time, at the current rate of vaccinations, before the inoculation of the Phase 2b cohort, the balance of the population aged between 18 and 49, begins.

By the time that stage of the rollout commences, with any luck additional Pfizer doses will have started to arrive and Novavax should have been approved.

In the meantime, Australia remains a good place to be. Not only is there no community transmission, there is also what Ms Halton described as the "fantastic luxury" of being able to go to the pub, to go out for a meal, and even to go to the football.

Life here, even with these setbacks, is far closer to "normal" than what the vast majority of the global population is experiencing.

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