The three-year programme, which is part of a partnership between the charity Rotary and UNICEF, the UN children's agency, involves delivering vaccines for rotavirus and pneumococcal disease, while teenage girls will also be immunised to protect them from cervical cancer.
The vaccine rollout will run in Nauru, as well as Vanuatu, Samoa, Tonga, Tuvalu, the Cook Islands, Kiribati, Niue and Palau.
Work has started in Nauru, where Mizuli Apadinuwe's 14-year old daughter received the human papillomavirus vaccine that protects against cervical cancer.
"I'm grateful that my daughter is able to get this vaccine. So in the future it prevents her from [contracting] cervical cancer," she said.
UNICEF Australia's Libby Hodgson said they want to protect kids from potentially life threatening illnesses.
"The vaccines will protect against preventable childhood diseases such as rotavirus, meningitis and forms of pneumonia, as well as the HPV vaccine, which will be available to adolescents and protects against cervical cancer," she said.
Health experts say pneumonia and diarrhoea are two of the top killers of kids under five in the Pacific, while cervical cancer rates are also high across the region.
Fiji doctor Frances Vulivuli, who is also UNICEF's Pacific health and nutrition specialist, said it was an important initiative because they regularly see children with complications resulting from pneumonia and diarrhoea.
"It's quite common. Every day, in the clinics across the Pacific, we expect to be seeing children presenting with symptoms of severe pneumonia or diarrhoea," Dr Vulivuli said.
Health workers hope these vaccines will help reduce their workload in the long term.
The Australian arm of the charity Rotary is fully funding the vaccine programme in some of the countries and partly funding it in others.
Rotary's spokesperson and project director, James Allen, said many Australians and New Zealanders chipped in to make it possible.
"Rotary is looking to raise about AUD$4 million (US$2.8 million) for this. We're currently something over $2 million (US$1.4 million) that we've already raised so we're well over halfway. And that's been enough to get the programme going. But we still have some work to do," he said.
He hopes the three vaccines will become part of each country's regular childhood immunisation programme over time.
"Once we get over the...initial three to four-year programme to introduce these vaccines, they will become part of the standard vaccination programs in these countries," he said.
"It's really all about giving these countries the capabilities that they need to do this sustainably. So these vaccines will become part of the standard immunisation programmes in the countries," he said