Australia has not received 3 million doses of AstraZeneca's COVID-19 vaccine that was previously promised to the country.
The acting chief medical officer confirmed the major gap in Australia's vaccination drive to local media on Tuesday.
Due to export curbs by the European Union in the wake of the the drugmaker's failure to meet its shipment pledge, Australia only vaccinated 670,000 by the end of March, falling dramatically short of its previous pledge of 4 million first doses.
Australia began vaccinations much later than some other countries due to low case numbers.
Most of Australia's near 26 million population will receive the AstraZeneca vaccine, as local production of the vaccine also steps up.
About 2.5 million doses have been locally produced so far.
The country's pharmacy guild has also blamed the slow rollout on a lack of co-ordination between the Australian national government and states.