The rollout of Australia's COVID-19 vaccination program is set to start next month, and while regulators were in a race to determine if the frontrunners were safe and effective, it was likely many questions about the vaccines would take years to answer.
Australia's initial vaccine rollout plan included 10 million doses of the Pfizer vaccine and 53 million doses of the AstraZeneca vaccine, but the government has signed deals with other manufacturers and was in talks with at least a dozen more.
Pfizer and AstraZeneca have entered a provisional determination process with the Therapeutic Goods Administration, meaning the initial approval would include advice for particular groups, such as children or pregnant women, and acknowledge what information was not yet known.
If there was a risk to certain groups, "that information will be front and centre in the information going to patients," said the head of the Therapeutic Goods Administration John Skerritt.
Professor Skerritt has also signalled advice could change as more information was gathered from around the world, where other countries had already begun their rollouts.
Many of the vaccine candidates for COVID-19 had been trialled using two doses to create the right immune response.
In the United Kingdom the AstraZeneca vaccine was being rolled out with a gap of 12 weeks before the first and second shot, a decision made in an attempt to get as many people vaccinated as quickly as possible. It was not yet clear what effect this would have on the efficacy of the vaccine, but Australian authorities were keeping a close eye on the results.
"What we will see emerge over the coming months is more and more evidence about whether leaving four weeks, eight weeks, 12 weeks is best," Prof Skerritt said.
"At the moment, most of the evidence - there's hints longer might be better - but it's not robust enough."
Prof Skerritt said Australians shouldn't be surprised if the regulator's advice about the vaccines was "tweaked" after the initial approval, as more evidence came to hand.
"Even if we do approve the AstraZeneca vaccine in February, we may in June or July, when there's more evidence, say, 'Actually, the recommendation is now 12 weeks not four weeks', and that's keeping up-to-date with the best evidence," Prof Skerritt said.
"We do that all the time with vaccines and medicines ... it's not just at one point in time and that's the decision and it's forever."
Australia's regulator was currently in a sprint in hopes to approve the Pfizer vaccine this month, but Prof Skerritt said the job would not be over after initial approval, despite already having more than 10,000 pages of data.
"We know that we'll continue to get data, both on safety but also how well the vaccines work, for a very long period in the future," he said.