Apple will require retail and corporate employees to provide proof of a COVID-19 booster shot to enter the workplace, The Verge reported on Saturday, citing an internal email.

Starting January 24, unvaccinated employees or those who haven't submitted proof of vaccination will need negative COVID-19 tests to enter Apple workplaces, the report said. The Verge said it was not immediately clear if the testing requirement applies to both corporate and retail employees.

Eligible employees will have four weeks to complete the booster dose regime; otherwise, they too will have to take the rapid test before entering an Apple area.

"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," the memo read, according to The Verge.

Apple did not immediately respond to a request for comment.

Many companies in the U.S. have been strengthening their COVID-19 rules, mandating vaccination and delaying back-to-office plans as the Omicron variant increases infections across the country.

Earlier on Monday this week, Facebook's parent Meta Platforms mandated COVID-19 booster shots for all workers returning to offices. It also delayed U.S. office re-openings to March 28, from an earlier plan of January 31, the company said.

Alphabet Inc's Google on Friday said it was temporarily mandating weekly COVID-19 tests for people entering its U.S. offices. 

A report by The Information said Amazon has offered its U.S. warehouse workers $40 to get a booster shot.

(With input from Reuters)