Some of the UK's biggest supermarket chains have urged customers not to panic buy amid the "pingdemic" after pictures of empty shelves appeared on social media.
Iceland, Co-op and Sainsbury's bosses said they are continuing to receive regular deliveries - and that there is no need for customers to change their shopping habits.
With images posted widely on social media, the supermarkets described any shortages as "patchy", adding that gaps on the shelves were "temporary" as they awaited deliveries, and were occurring in pockets rather than across supply chains.
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The "pingdemic", the shortage of HGV drivers and the hot weather were all contributing to delivery glitches, grocers said, while stressing to consumers that panic buying would create a problem that did not exist, as PA reports.
This morning, it was revealed that a record 618,903 alerts had been sent to users of the Covid-19 app in the week to July 14, telling them to self-isolate.
A Co-op spokesman said: "We are sorry that we are running low on some products. Like many retailers, we are impacted by some patchy disruption to our deliveries and store operations but we are working closely with our suppliers to get re-stocked quickly."
A Sainsbury's spokeswoman said: "We are working hard to ensure customers can find what they need.
"While we might not always have the exact product a customer is looking for in every store, large quantities of products are being delivered to stores daily and our colleagues are focused on getting them on to the shelves as quickly as they can."
Tesco confirmed that it had plenty of food and deliveries arriving across the UK every day.
However sporadic disruption from the industry-wide shortage of HGV drivers and an increase in staff self-isolating on a precautionary basis was leading to pockets of temporary low availability across a small number of products.
Iceland managing director Richard Walker has said staff absence rates are now double the usual number, with the figure rising 50% "week on week" due to people being told to self-isolate by the NHS app.
Mr Walker told the Radio 4's Today programme: "We've now got over 1,000 staff off, who've been pinged. That's double the normal rates, and it's rising at 50% week on week.
"Our big concern is that we've kept all of our shops open throughout the pandemic, but now we have had to close one or two shops and reduce hours in others.
"But that could get a lot worse a lot quicker, unless the country's system is sorted out."
Mr Walker urged shoppers not to panic buy, saying: "There is certainly no problem with supply of stock.
"Panic-buying is only an option for those who can afford it and it often means that others go without."
Elsewhere, sandwich chain Pret A Manger has temporarily closed 17 shops due to staff being forced to self-isolate.
The head of the British Retail Consortium, Helen Dickinson, has suggested rules around self-isolation could be amended for people working in food supply chains following rising levels of staff absence.
Ms Dickinson suggested to BBC Breakfast that bringing forward the date double-vaccinated people will not need to self-isolate if they come into contact with a Covid-19 case could be one solution.
"There are some pilots for tested release for businesses and people who get paid to test themselves and then released back into their workplace, those pilots could be extended or that could be a new system," Ms Dickinson said.
