University of Sydney epidemiologist Dr Fiona Stanaway said, given no COVID-19 vaccine was 100 per cent effective, it was to be expected that some people who had been vaccinated would test positive although they would most likely be asymptomatic.
If youre asymptomatic, youre less likely to transmit, she said, adding the figures regardless show that hotel quarantine systems were still needed.
When you have a country like Australia where most people are unvaccinated, so theres a risk of a mass outbreak, people still need to do hotel quarantine, she said.
Its not a matter of them getting sick, because they probably wont. Its about whether they could transmit.
As of Friday, a total of 590,194 NSW residents had received at least their first dose of a COVID-19 vaccine through NSW Health, a Commonwealth provider or the GP network.
Within that group, 75,187 frontline health and quarantine workers and their families had also received their second dose.
NSW recorded 180 overseas acquired cases in the four weeks to May 1, its highest figure since four-weekly totals started to be published last October.
Eighty-nine of the group had travelled from India, 15 from the US and 14 from Bangladesh.
The percentage of returned overseas travellers in NSW testing positive to COVID-19 dropped substantially between April 24 and May 1.
In the week ending April 24, 0.8 per cent of returned overseas travellers tested positive, the highest rate recorded this year. By May 1, following the first days of the federal governments temporary Indian flight ban, it had dropped to below 0.6 per cent.
Health advice to national cabinet is that hotel quarantine systems can cope with a positive rate of up to 2 per cent, although NSW Chief Health Officer Kerry Chant has previously said the figure is not necessarily applicable in her state because positive travellers are moved into a separate health hotel system.
On Friday, Premier Gladys Berejiklian told Today it was possible the source of infection of an eastern suburbs couple earlier this week, the states first infections outside the quarantine system in more than a month and a trigger for restrictions over the Mothers Day weekend, would never be found.
The Premier expressed concern that at least one person, possibly more, had been walking around with the virus but said the days figures meant Sydneysiders should not be bracing for a lockdown at this stage.
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This comes as the mystery of how an eastern suburbs couple caught a COVID-19 infection brought into hotel quarantine by a US traveller remains unsolved.
