The Canterbury A&P Show has been cancelled for the second year in a row.
Around 100,000 people normally attend, with many rural business trading at the event.
The event is one of three that make up the Cup and Show Week in November. The A&P show, Addington Cup Week and Riccarton Park Races were projected to bring in more than $4m of visitor spending and 22,275 visitor nights.
Joanna Norris, chief executive of the city's economic development ageny ChristchurchNZ, said it was a massive loss for the city and region.
"The government's health-based approach to Covid-19 is essential and we absolutely support it.
"However, businesses and the major events sector need a clear outline of the pathway to lower alert levels in the South Island.
"Protecting the lives of New Zealanders is of primary importance, however sustaining safe community and economic activity in the South Island is also of huge importance."
ChristchurchNZ and the show asked the government to allow the outdoor event to trial a vaccine certificate programme but couldn't get approval in time, Norris said.
Just a few days ago organisers of the Canterbury show were still hoping it would go ahead. General manager Tracy Ahern said at the time there was a real recognition people have had a tough time and the event would bring the region's communities together.
The Hawke's Bay A&P Show, scheduled for this month, was cancelled due to the uncertainty and risks associated with the Delta outbreak.
ChristchurchNZ has thrown its support behind the 90 percent for Canterbury campaign which aims to surpass 90 percent vaccinations for eligible Cantabrians by Labour Day.
Norris said that would provide more confidence for large-scale events to be held.