All its stores will only open to these two groups for the first hour of trading on Thursday, chief executive Mike Coupe said, but will open for an hour longer so other shoppers do not miss out.
Supermarkets have seen a huge surge in demand for delivery services, with no slots available until next month for both Tesco and Waitrose in some parts of the south east.
The surge came as Transport Secretary Grant Shapps authorised a temporary relaxation of the drivers’ hours rules to help deliver goods to stores across the country.
Iceland outlets across the country have also introduced reserved time slots to give the vulnerable and the elderly a chance to shop in store.
Sainsbury’s has now said customers over 70 and those with a disability will also have priority access to online delivery slots from Monday and the chain is also expanding its “click and collect” service.
Mr Coupe added that as of Thursday, Sainsbury’s will be closing its cafes and its meat, fish and pizza counters to free up freight capacity for essential products.
Customers will also only be able to buy a maximum of three of any grocery product and a maximum of two on the most popular items such as toilet roll, soap and UHT milk from Wednesday onward.
“As we work to feed the nation, we are also focusing all of our efforts on getting as much food and other essential items from our suppliers, into our warehouses and onto shelves as we possibly can”, Mr Coupe said.
“We still have enough food for everyone – if we all just buy what we need for us and our families.”
Tesco has had to bring in similar purchasing restrictions to curb panic buying, particularly on anti-bacterial wipes, dried past and toilet roll.
It was forced to take its mobile app offline temporarily due to high demand on Tuesday, and announced it would be reducing the hours of all of its 24-hour stores to 6am to 10pm.
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A spokeswoman said: “It gives our colleagues the time overnight to restock the store, replenish the shelves and support our online grocery service at a time when demand is high.”
Elsewhere, rival Morrisons announced on Tuesday it is creating 3,500 jobs to meet surging demand for its home delivery service caused by the pandemic.
The chain said it would be recruiting 2,500 pickers and drivers while hiring about 1,000 people to work in distribution centres.
It is also planning a new call centre for those without access to online shopping, plus the launch of a new range of simple-to-order food parcels from next Monday.