As new COVID-19 new infections and deaths in the U.S. continue to march downward, companies are having to make a difficult choice: Stay at home or back to business as usual? For drugmaker AbbVie, this week marks a return to normal for part of its workforce—but some employees have their reservations.

AbbVie ordered a slew of employees to return to work Monday despite the ongoing risk of COVID-19 infections in an effort to reintroduce the "face-to-face" work environment the drugmaker values, according to an Aug. 27 email to employees reported by CNBC. 

With employees reportedly skeptical about returning to their workplaces, Illinois-based AbbVie is moving forward with a phased approach to bringing employees back, months after a sweep of lockdowns back in March. 

The company's third phase of its restart plan allowed workers in R&D, sales and marketing to return to onsite work on a voluntary basis back in July, CNBC reported. Today, that voluntary order became mandatory.

RELATED: Biogen conference likely linked to 'tens of thousands' of COVID-19 cases, researchers say

AbbVie reportedly has been phasing executives and manufacturing employees back to work sites since June on a rotating, part-time basis, and it plans to eventually bring all workers back on site as part of the fourth and final phase of the program, which has yet to be announced. 

In interviews with CNBC, employees said they were concerned about resuming normal work days despite precautions AbbVie put in place to prevent infections. Particularly for employees with pre-existing conditions, that's a big risk as some believe working remotely has been sufficient, CNBC said. 

An AbbVie spokeswoman could not be reached for comment by press time. 

RELATED: With meeting case count rising above 70, Biogen tells attendees to prep for quarantine, isolate from loved ones 

As AbbVie takes the plunge to restart business as usual, employees may take a lesson from Biogen after a company conference in the early days of the pandemic was linked to thousands of COVID-19 infections. 

Last month, the Boston Globe reported Biogen's February management conference was connected to cases in numerous states and countries, including about 20,000 cases in the Boston area alone. 

Researchers identified two specific COVID-19 mutations associated with cases among conference attendees. The team then sequenced virus genomes of 772 coronavirus patients in the Boston area and found the conference-associated mutations in 289 of them, including 122 people at homeless shelters. 

A Biogen spokesperson told the Washington Post in August that the company had complied with health guidelines when it held the conference. Further, the February event took place “when general knowledge about the coronavirus was limited,” and the company informed experts as soon as it was aware of the outbreak.