The organisation is currently dealing with 20-plus positive cases across the performing company, crew and administration.
"Up until three weeks ago, we'd never had a case of COVID at Opera Australia," CEO Fiona Allan said.
"But over the last 10 days we've had multiple cases a day."
Nevertheless, the company intends to proceed with its summer season in Sydney, opening three operas in January.
La Boheme will now start on January 4, Turandot is due to open on January 12, while The Marriage of Figaro is set to open on January 27.
"We've thought through all the different contingencies and are putting all our efforts into keeping our company as safe as we can be and starting the 2022 season with La Boheme," Allan said.
"We just need to work through it a day at a time, performance by performance."
Allan welcomed national cabinet's announcement on Thursday of a new federal definition of a close contact.
"That will make business interruption much easier to manage, and in turn make it easier for business to continue," she said.
Seeking to reassure nervous audiences, Allan reiterated that everyone entering the Sydney Opera House must be double-vaccinated, or have an exemption, and wear a mask at all times, unless eating or drinking.
"The Joan Sutherland Theatre has good continuous air-flow going in and out, and there have been no known cases of COVID transmission in theatres," she said.
Ticket holders to La Boheme on New Year's Eve will be offered credit vouchers or full refunds.
