More than 650 people across Australia, including 72 in Canberra, were part of a phase two clinical trial for the Novavax vaccine against COVID-19 last year, and many now have questions about whether it is safe or advised to get another type of vaccine, or whether their original jab will one day be recognised on potential vaccine passports.

A spokesman for the Department of Health has confirmed the Australian Immunisation Register had "well-established processes" to record details of people who have participated in vaccine trials, including for some COVID-19 trials.

The Register currently only records details of the AstraZeneca and Pfizer vaccines as they are the only ones registered for use in Australia.

"If there is a future need for COVID-19 vaccine trial details to be recorded on the AIR, particularly to support any proof of vaccination requirements, the Department of Health will seek advice from the Australian Technical Advisory Group on Immunisation (ATAGI) as appropriate, and implement any necessary system changes to the AIR," the spokesman said.

The Australian advice follows trial participants in the United Kingdom threatening to pull out because their jabs were not recognised on the passport app in that country, preventing travel to and from Europe.

Australian participants in the trial say they have been left in the dark about how their vaccination could be recognised, and whether it would be safe to mix the vaccine with the two currently approved in Australia, or if they could be left unprotected if they don't get an extra jab.

Under the trial, participants were given their first jab in September last year, with a second dose 21 days later. According to Novavax, there were five different groups in the trial.

Group one received a placebo at both injections; group two received a single 5 microgram dose, group three received two 5 microgram doses; group four received a single 25 microgram dose and group five received two 25 microgram doses.

Some of the participants also received a third 5 microgram dose six months after the initial injection.

A phase three trial of the vaccine that has wrapped up in the United Kingdom gave people two 5 microgram doses of the vaccine 21 days apart.

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In March this year, participants in Australia were given the option to be "unblinded" meaning they could find out what they were given as part of the trial. One participant who found they had been given a single 25 microgram dose, said the only advice given on whether to get the AstraZeneca or Pfizer vaccine was to speak to a GP.

"I'm just so confused," the participant told The Canberra Times, thinking it unlikely a GP would know all the details of all the clinical trials to date.

Another participant chose to be unblinded and found they had been given two placebo doses, making it an easier choice to get the AstraZeneca jab when they became eligible.

In a statement, a spokeswoman for Novavax said the data available showed the two doses were likely to be "protective against illness due to SARS-CoV-2".

"That said, the Novavax vaccine has not been authorised for use yet in Australia by the TGA. Therefore, participants who have received two doses of the vaccine should discuss with their healthcare provider the option of receiving an authorised vaccine," the statement continued.

"For participants who have received a single dose of vaccine, emerging evidence for other vaccines suggest that a single dose may not provide optimal protection.

"As a result, participants who have received a single dose of the vaccine should discuss with their healthcare provider the option of receiving an authorised vaccine."

In the statement, the company left the decision about further vaccinations up to participants and their healthcare provider.

The Health Department spokesman said it was too soon to advise participants on further vaccinations.

"It is too soon to determine what, if any, additional vaccinations may be required for individuals who have participated in any clinical trials, unless it is known that they only received a placebo," the statement said.

"If an individual participating in a clinical trial is found to not have received an adequate degree of protection from COVID-19 the government will follow the guidance of the TGA and ATAGI on what if any additional vaccinations are recommended."

Novavax is an American company and phase three clinical trials of its vaccine against the virus are still running.

The jab uses a different technique to create immunity from the two already available in Australia.

The government here has ordered 51 million doses of the company's vaccine, which is expected to need two doses and arrive later this year, pending further results and regulatory approval.

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