Australian Prime Minister Scott Morrison announced the doses would be sent immediately, along with other critical care equipment.
Papua New Guinea's fragile healthcare system is under huge strain.
Officially, there are 1,400 active cases in the country, but the true number is thought to be much higher.
Testing has been an issue for the island nation. As of 10 March, only 50,000 tests had been carried out in a country with a population of nine million.
However, Australian officials said that of the areas tested in the past week, almost half of the results had come back positive, including many healthcare workers.
Port Moresby Hospital's Covid-19 isolation ward is reportedly full and additional beds are filling up rapidly. Dozens of medical workers have also tested positive for Covid, and more than half of the nation's total of 2,269 cases have been reported in the past month alone.
"The number is quite staggering, if we don't do [a] corrective response to this, our health system will be clogged," Prime Minister James Marape told journalists on Monday.
He has urged citizens to "remain in your provinces, remain in your villages, remain in your districts".
"It's broken loose … we need to contain it," he said, according to the Australian Broadcasting Corporation.
During a news conference on Tuesday, Mr Morrison said the vaccine doses - from Australia's own stocks- would be used to vaccinate health workers.
He also said that he had lodged a request with AstraZeneca and the European Union to access one million of the country's contracted doses, "not for Australia, but for PNG, a developing country in desperate need of these vaccines".
It's unclear when these vaccines would be delivered. Papua New Guinea's first batch of vaccines were set to arrive in April as part of the global Covax inoculation sharing scheme but experts warned this would be too late.
Infectious diseases expert Sanjaya Senanayake, from the Australian National University, told the BBC that Australia's 8,000 doses would prove helpful, even though it can only protect 4,000 people.
"You can't possibly achieve herd immunity this way, but if they're used for healthcare workers and maybe any excess reserved for vulnerable groups, it'll still be helpful," he said.
The Australian state of Queensland is helping Papua New Guinea with testing. Authorities in the state said they had recorded 250 positive results out of 500 tests conducted.
There is also concern that the outbreak could spread to Australia, with Mr Morrison announcing the cancellation of charter flights and outbound travel to Papua New Guinea for the next two weeks.
He said that since Monday, Australian authorities had already found 32 cases from PNG in Queensland.