Healthcare and border workers who don't get the COVID-19 vaccine could lose their job - and such dismissals would be legally justified in some cases, one employment lawyer says.

It comes after Medsafe gave provisional approval to the Pfizer-BioNTech vaccine on Wednesday, but the Government has not disclosed when the shipment of 750,000 doses will arrive.

Aged care facility operators Ryman Healthcare, Oceania Healthcare, and Arvida will require all new employees to get the COVID-19 vaccine, but existing employees can decline.

"Part of our policy on hiring is that people agree to a vaccine and get their annual flu jab as well," Arvida chief financial officer Jeremy Nicoll says.

But a top employment lawyer says enforced immunisation could soon be commonplace for anyone taking up a high-risk job.

"There are employers that are seriously considering taking that step," Charlotte Parkhill, a partner at Dentons Kensington Swan, says.

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When asked if a company could say "no jab, no job", she says "yes they could" say that.

Health care workers tend to be pro-vaccine, but sanctions for not doing so don't sit well with unions.

"The most important thing is that [people's] employment isn't being jeopardised, or people aren't having punitive measures taken against them when they're existing staff," NZCTU secretary Melissa Ansell-Bridges says.

Some border-related companies have already asked for advice about getting their staff immunised. Air New Zealand won't say if its staff will have to be vaccinated, but the Government could get involved.

"As a Government, we will not be making it compulsory, however, for our frontline workers we will be considering whether or not we are meeting our health and safety obligations," Prime Minister Jacinda Ardern says.

Most of the big businesses Newshub spoke to on Wednesday say they will encourage vaccination. Two are allowing staff to make up their own minds - Fonterra and ANZ bank.

But this is a moral dilemma for them, and as yet Fletcher building and many others are still grappling with it.