Australians hoping to come home for Christmas may remain stuck overseas because they are not considered fully vaccinated if they have had different doses of approved vaccines.
Since the federal government announced international borders would reopen to fully vaccinated citizens, permanent residents and their families, some overseas have received conflicting advice about their immunisation status.
Tim and Sharyn Nilsen have been living in Vietnam for the past two years after becoming stranded during their travels.
Ms Nilsen told ABC Radio Brisbane they were only offered an AstraZeneca jab and Pfizer for the second shot during the country's vaccine rollout, partly because of a supply issue.
But Ms Nilsen said it was good to have had the mixed vaccines in order to be fully vaccinated, especially at a time when Ho Chi Min City was recording thousands of cases a day.
Mixed dose, mixed message
When the Australian government announced international borders would reopen, Ms Nilsen checked the Services Australia website and with the Australian embassy in Vietnam about vaccine certification.
The embassy told her that having two different vaccines was acceptable as long as they were approved varieties like AstraZeneca or Pfizer.
So she booked tickets to visit her and Mr Nilsen's parents in rural New South Wales, who they have not seen for almost two years.
"I went and booked a ticket and that was the Wednesday," Ms Nilsen said.
But on Friday, she received an update from the embassy that said the rules were changing constantly and people who had mixed shots would be considered "not vaccinated".
A day later, Singapore Airlines advised Ms Nilsen that the the flight had been designated as "For Eligible Passengers Only" (FEPO) and that mixed vaccines would not be recognised.
"[The Australian government is] jumping up and down saying, 'We're going to get Aussies home,'" Ms Nilsen said.
Singapore Airlines, Scoot and Vietnam Airlines all have statements on their websites that customers with mixed vaccine doses are not eligible at this stage.
Internationally, many countries, including Canada, Spain and South Korea, have introduced mixing doses of vaccines as part of their rollout.
While it does not recommend mixing jabs, the United States Centre for Disease Control and Prevention recently updated its guidelines to suggest travellers who have had mixed doses of US or World Health Organisation (WHO) approved vaccines be accepted.
Divide over issue remains
Katherine O'Brien, the director of the WHO's Department of Immunisation, Vaccines and Biologicals, recently said there was evidence combining an AstraZeneca vaccine dose with either of the MRNA vaccines, Pfizer or Moderna, could produce a "good" immunity response.
But Immunisation Coalition chair Rod Pearce said there were too few studies to be certain about the efficacy and safety of mixing vaccines.
Mater Hospital's infectious diseases director Paul Griffin said authorities should consider whether mixing vaccine doses could be approved.
"There's been a few clinical trials," he said.
The Australian Technical Advisory Group on Immunisation (ATAGI) recommends using the same COVID-19 vaccine for the two doses of the primary course.
"While there is emerging data about mixed dose schedules, larger studies and longer term follow up are required to confirm the safety of this approach," a spokesperson said.
ATAGI provides clinical advice on the use of a different COVID-19 vaccine as the second does in special circumstances.
"ATAGI continues to monitor and review the evidence for mixed COVID-19 vaccine schedules and provide updated recommendations to government as appropriate," the spokesperson said.
"Travellers that do not meet the definition of fully vaccinated may still be able to travel, but only under the rules of unvaccinated travel."
