The United Nations Childrens' Fund, or UNICEF, says it is working with the governments of Samoa and Fiji to keep children safe in the wake of Cyclone Evan.
It is providing oral rehydration salts and tetanus vaccine as well as assisting with a public information campaign promoting lifesaving messages.
UNICEF says water-borne diseases such as diarrhoea, leptospirosis and typhoid pose significant threats to children.
About 63,000 sachets of oral rehydration salts are being provided to the Ministry of Health in Fiji and 5,000 doses of tetanus toxoid vaccine to Samoa.
The rehydration salts provide a simple, inexpensive treatment to prevent dehydration from diarrhoea.
Meanwhile UNICEF NZ has launched an emergency appeal to support immediate relief efforts.