Three people have tested positive for the coronavirus despite having received the vaccination.
The three fully vaccinated people tested positive in Hawaii after receiving either the Moderna or Pfizer jabs.
Hawaii's health department said of those who had tested positive, one was a healthcare worker from Oahu who travelled to a number of US cities in February after receiving the jab in early January, the New York Post reported.
The Department of Health added however those who contracted the virus did not become severely ill or appear to transmit it to others.
"The really important thing is that being vaccinated prevents us from serious illness, hospitalisation and death," Department of Health Director Dr Elizabeth Char said on Covid communication platform The Weekly Dose.
"That's what we really need the vaccines to do for us.
"We have seen cases where people are fully vaccinated, and we have some cases in Hawaii now where people got vaccinated... travelled to the mainland, and we think they got ill on the mainland.
"Thankfully, their symptoms were very mild, which is exactly the protection the vaccine affords, but you can get infected with Covid."
Australian-made vaccine to be rolled out
Australians can soon start being inoculated against Covid-19 using an Australian-made vaccine.
The nation's medicine regulator overnight approved more than 830,000 doses of Melbourne-made AstraZeneca vaccine, confirming they are of the same quality as those made overseas.
"Testing of the vaccine batches in our Canberra laboratories plus review of extensive manufacturing documentation, has ensured that the locally-manufactured vaccine has exactly the same composition and performance as the overseas-manufactured vaccine," the Therapeutic Goods Administrations said in a statement.
"We will now be able to provide secure access to large numbers of doses of a domestically-produced vaccine, with the Australian government having procured 50 million doses for delivery in the coming months."
The approval is a shot in the arm for the federal government's vaccination rollout, which has copped criticism for slow progress.
The locally-produced AstraZeneca doses will be used as part of the 'phase 1b' vaccination program which started on Monday and will be available at more than 4000 providers including GP clinics and official health services.
"(Regulatory) approval is required for each and every batch of any vaccine supplied in Australia," the administration said.
"All subsequent batches of the Melbourne-manufactured vaccine completed in the coming weeks and months will go through the same individual batch testing and release process."
CSL's Melbourne facilities are producing 50 million doses of the AstraZeneca vaccine.
So far 62,000 people within the aged care sector have received the vaccine.
Phase 1b will see six million Australians get their jabs, mostly via GP clinics.
The program takes in everyone over the age of 70, along with Indigenous Australians over 55 and younger adults with a medical condition or disability.
Workers deemed critical or high risk can also apply.
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