New South Wales Health has revealed six overseas travellers who reported being fully vaccinated have tested positive to Covid-19 in hotel quarantine.
The numbers were released in this week's NSW Health Covid-19 surveillance report as the federal government pushes forward with its vaccine passport plans.
The report states six people in the NSW hotel quarantine system tested positive over four weeks ending on May 1, despite reporting they were vaccinated before landing in Australia.
The figures raise concerns about the prospects of a vaccine passport system as Prime Minister Scott Morrison comes under increasing pressure to repatriate Australians stranded overseas.
NSW Health noted all six might have contracted the potentially deadly virus before their vaccination becoming fully effective.
The report stated a dose does not become fully effective until two weeks after the patient receives the second of a two-dose vaccine.
Morrison this week said his government was working on a prospective vaccine passport system, which would allow those with the jab to travel more freely.
He noted a condition of such a system would be proof that vaccines protect travellers against the transmission of the virus.
The prime minister also expressed concerns about the effectiveness of home isolation.
Morrison's vaccine passport comments came as he said that the government was set to lift its India travel ban on May 15.
He described the ban as a "pause" and said it would end on its intended date, with repatriation flights to begin after that.
The ban made it unlawful for people to return to Australia if they had been in India in the 14 days prior.
There are currently 9000 Australians in India who want to come home, including 173 children who are in the country without their parents, a Senate committee heard this week.