Big tech firms are altering their return-to-work plans for employees, as Covid-19 cases rise in the US - with some stipulating that staff working in the office must be vaccinated, BBC reported.
The company joined Facebook in saying it would require US workers returning to the office to be vaccinated.
Twitter said it would pause office re-opening, closing offices in San Francisco and New York once again.
The two Twitter offices had been operating at up to 50% capacity for staff who wanted to return.
In a statement, the company wrote that it was "continuing to closely monitor local conditions and make necessary changes that prioritise the health and safety of our Tweeps".
Twitter said it remained committed to giving employees the option to work from home where possible.
Apple has reportedly delayed a planned return to on-site working until October.