Its boss Mike Coupe said socially-distanced queues were likely to remain "for the foreseeable future".
In a trading update, the supermarket said it saw huge demand for groceries in March as concerned shoppers stockpiled goods.
In common with other retailers, the UK's second-largest supermarket chain has brought in a number of measures in an attempt to keep customers and staff safe during the pandemic, as well as cope with the surge in demand for food.
They included installing screens at tills, increasing cleaning and recruiting thousands of temporary staff to work in-store, as drivers and in warehouses.
Sainsbury's said that those additional costs, as well as weaker demand for clothing and fuel, could result in a £500 million hit to its profits.