Vaccinators at a mass clinic in Auckland hope to get through about 11,500 bookings today and tomorrow.
About 4700 people received their first Pfizer shot yesterday - on the first day of the event.
A dozen vaccinators - each of them trying to average a jab every 90 seconds - are working across 240 booths set up at the Manukau Events Centre.
Coordinators say Auckland's largest previous vaccination clinics handled about 1000 bookings a day.
Patients are being bussed to the events centre from the Manukau Institute of Technology.
More than 16,000 people have booked into the mass vaccination event and the event is fully booked so no walk-ins are allowed.
Yesterday some people reported an hour-long wait before they were able to get their vaccination with long queues to register and then to get on the shuttle buses.
A repeat event for second doses is planned for 10, 11 and 12 September.