Britain is rushing 4 million Pfizer doses to Australia, where authorities are scrambling to bolster supplies of that Covid-19 vaccine and protect the population against a rapidly spreading outbreak of the delta variant.

The swap deal announced Friday follows Australian deals with Singapore and Poland to address a short-term Pfizer shortage.

Prime Minister Scott Morrison said the British shots would leave Britain on Saturday and double Australia’s Pfizer supplies in September.

Australia was keen to make more vaccine deals with other governments, Morrison said.

“I said I would leave no stone unturned and I can tell you I’ve been turning over some stones in recent times to ensure that we can progress the vaccination program as quickly as we possibly can,” Morrison said.

“Thanks Boris, I owe you a beer,” he added, referring to his British counterpart Boris Johnson.

Australia has particularly low vaccination levels compared to other wealthy nations, with only 36% of Australians aged 16 and older fully vaccinated.

The Australian government has been criticized for failing to strike more vaccine deals with manufacturers. Australia had planned to manufacture most of the vaccine for its 26 million people, including 20 million adults.

But one home-grown vaccine was abandoned during development because it produced false positive results to HIV tests. Locally-produced AstraZeneca, which is the only alternative to Pfizer registered for use in Australia so far, proved unpopular with many due to changing medical advice on the risk of blood clots. Australia initially bought only 10 million Pfizer doses but has increased the order to 40 million shots this year.

The first of 10 million shots of the Moderna vaccine is expected to become available soon.

The need for vaccines comes as Australia’s most populous state, New South Wales, on Friday reported its deadliest day of the pandemic with 12 fatalities and a record 1,431 new infections. The state government predicted the daily death toll will peak next month if the pace of vaccination is maintained.

The state government plans to triple the number of intensive care unit beds and staff in October when the number of COVID-19 patients are expected to peak, New South Wales Premier Gladys Berejiklian said.

She expects 70% of the population aged 16 and older in her state will be fully vaccinated by mid-October.

The outbreak that began in Sydney in June has spread to Melbourne, Australia’s second-most populous city and the capital of Victoria state.

Victoria reported 208 new infections in the last 24 hours and a single death.

New South Wales and Victoria are in lockdown and see increased vaccinations as the only way to safely ease pandemic restrictions.

The Australia Capital Territory still hopes that its lockdown will stamp out delta. The rest of Australia remains virtually free of the virus.

Singapore delivered 500,000 Pfizer shots to Sydney on Thursday. Australia must repay Singapore and Britain with equivalent numbers of doses in December.

Australia bought 1 million Pfizer doses from Poland for an undisclosed price in August.

The Australian government hopes the states will end pandemic lockdowns once 80% of the population aged 16 and older was fully vaccinated.