Apple is now asking all staff to provide proof of having had the COVID-19 booster jab.
Amid a surge in Omicron cases, the tech giant is giving their employees a four-week window to comply once they are eligible for a booster shot.
Those who are unvaccinated will have to test negative using rapid antigen tests before entering the workplace beginning on January 24.
An email sent to employees and obtained by The Verge read: “Due to waning efficacy of the primary series of COVID-19 vaccines and the emergence of highly transmissible variants such as Omicron, a booster shot is now part of staying up to date with your COVID-19 vaccination to protect against severe disease."
In October, Apple required employees who haven't been inoculated against the virus to provide a negative test result every time they work in one of their offices, while retail workers tested twice a week.
Staff were encouraged to work from home at the height of the pandemic and through much of 2021.