New Zealand could be just a day away from approving a Covid 19 vaccine -- but it may not be immune to the global vaccine shortage

Medsafe will receive advice on the Pfizer vaccine from the Medicines Assessment Advisory Committee today, and could give the vaccine provisional approval by as early as tomorrow.

But it's still unclear if New Zealand will be affected by overseas delays to vaccine production.

World Health Organisation chief scientist Soumya Swaminathan says manufacturers will struggle to meet demand, unless they're willing to collaborate.

She says manufacturing at the scale required will be an unprecedented challenge.

The Government is currently planning to vaccinate border workers, in the first half of this year.