The Maritime Union says it's uncertain whether all port crews that need to be vaccinated will be by the end of the month.
All port workers who board international ships need to have at least one dose of the Covid-19 vaccine by next Thursday.
The Ministry of Health's Covid-19 vaccination operations group manager Astrid Koornneef said as of Monday September 20 at 9pm, 90 per cent of the total 2,891 port workers (both Government and privately-employed) had received at least one dose.
Of that number, 2,143 were fully vaccinated, and 461 had only one dose.
"All privately employed border workers have until September 30 to have their first vaccination, while Government employed workers had until August 26 to receive their first vaccination," Korrnneef said.
"Any workers not vaccinated after these dates need to discuss options with their employer.
"Work to vaccinate all remaining privately employed border workers by the end of September (as required under the amended border work requirements) is progressing well, with all DHBs with major ports in their regions continuing to actively work to further improve vaccination rates."
Examples of the range of initiatives underway included additional pop-up vaccination sites at flexible times that align with shipping schedules and workers' shifts, education sessions involving nurses and other health professionals to ensure workers have reliable, up to date information, outreach sites offering testing as well as vaccinations, easier booking processes for workers and their families, mobile vaccination teams at ports and vaccination events.
But the Maritime Union of New Zealand's national secretary Craig Harrison said misinformation was being shared.
"It's not a sure bet, until we hit that date you really just don't know where a lot of people are going to land with it. People might've for instance booked a vaccine - that doesn't mean they're going to go and get it."