Samoa has restricted entry of all travelers, unless approved by the Samoan government due to exceptional circumstances, e.g. repatriation.
All travelers from outside of New Zealand must spend 28 days in New Zealand before onward travel to Samoa and must comply with all requirements. All passengers entering Samoa from New Zealand will be quarantined for 14 days at a designated facility.
Children under the age of 2 are exempt from presenting a COVID-19 test.
Travelers with proof of recovery from the virus within the last 90 days prior to boarding. Proof of a recent positive viral test and a letter from your healthcare provider or a public health official stating that you were cleared to travel.
More info at the CDC site
Travelers who did not get tested, are advised to stay home and self-quarantine for 10 days after travel.