The other two spots will be filled by Michaella Krajieck, of the Netherlands, and Croatian 17-year-old Petra Matic.
Traditionally, all four berths go to New Zealanders but a thinning depth reduced the options for organisers, while Cantabrian Ellen Barry and Aucklander Sasha Jones both declined invitations.
World No 320 Barry is recovering from a wrist injury, while Florida-based Jones somewhat unusually decided her priorities were elsewhere.
Hollands (25), of Otago, has dominated recent New Zealand domestic tournaments, winning five titles including the New Zealand residentials last week.
Vano (19) has a WTA ranking of 686.
World No 219 Krajieck is on the comeback trail after an injury-plagued year.
She has been ranked as high as 30 and was the fourth seed at this year's ASB Classic.
Matic is rated one of the world's premier young players.
