Covid-19 jabs already given to millions of people around the world will factor into Medsafe's decision about whether to approve the Pfizer vaccine here.
Its Medicines Assessment Advisory Committee will meet tomorrow to review clinical data from trials and real world use.
If they give it the nod, the government will then have final approval, with that decision likely on Wednesday.
Experts say if it is granted the vaccine will be a monumental milestone in New Zealand's Covid-19 battle.
Health correspondent Rowan Quinn asked Medsafe Group Manager Chris James about what might be some reasons for a vaccine not making the cut.