But yesterday, he flew back with his godfather, Mark Wendt, who said an Auckland clinic refused to immunise the young boy because he didn't have a New Zealand passport.
Ardern said this was not acceptable.
She said anyone who heard about this issue would agree that it simply does not make sense.
"The fact that we didn't assist one child in New Zealand when we are giving vaccinations to Samoa to vaccinate feels nonsensical to me.
"So I will follow up with the Minister of Health."
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Then, unprompted, she said she was also "horrified" by a cartoon that ran in the Otago Daily Times (ODT) this week.
The cartoon depicted two women walking out of a travel agency with the caption: "I asked 'what are the least popular spots at the moment." She said 'The ones people are picking up in Samoa'".
The ODT has apologised for publishing the cartoon, which has been labelled racist.
"The content and the timing of the cartoon were insensitive, and we apologise without reservation for publishing it," ODT editor Barry Stewart said in a statement.
Ardern was clearly upset by the cartoon.
"This is affecting children and babies – it's absolutely horrific. No one takes it lightly, New Zealand is doing all we can to assist."