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.