Face shield minimizes spread of SARS-CoV-2, hospital-acquired infections

Wearing of face shields proves golden as a preventive measure, reducing not only the number of SARS-CoV-2 infections but also that of hospital-acquired infections (HAIs) among healthcare personnel (HCPs), as shown in a study reported at the 2020 virtual ID Week meeting.

At one hospital in Texas, US, the weekly positivity rate for SARS-CoV-2 rose from 0 percent to 12.9 percent in the preintervention period (April 17–July 5), then fell sharply to 2.3 percent following the implementation of universal face shield wearing (July 6–26). [IDWeek 2020, LB-16]

HAI cases followed the same pattern, increasing from 0 to 5 in the preintervention period and dropping back to 0 during the intervention period.

These favourable results may be attributed to a reduction in viral transmission, according to presenting author Dr Mayar Al Mohajer from the Baylor College of Medicine in Houston.

Al Mohajer pointed out that in their 500-bed hospital with more than 8,000 HCPs, they had instituted several preventive measures between April 1 and 17. HCPs and patients alike masked up. High-risk HCPs underwent surveillance testing every 2 weeks, while patients did on admission and prior to invasive procedures. Cluster units were also tested weekly.

Not long after, Texas began its reopening, which it did in three phases. By June 12, at the last phase, restaurants were operating at 75 percent of its capacity while college and professional sports capacity were increased to 50 percent, along with other facilities that were open. During this period, 112 HCPs tested positive for SARS-CoV-2, with the infection starting in the community then spreading staff to staff, Al Mohajer said. There were also seven HAIs recorded, which corresponded to 3.4 cases per 1,000 patient-days.

In response, on July 6, the hospital recommended that all HCPs wear a face shield upon entry to facility on the basis that face shields “reduce the potential of autoinoculation by preventing the wearer from touching their face” and “protect the portals of viral entry.”

Previous studies have shown that this measure effectively reduced immediate viral exposure by 96 percent when exposed within 18 inches of a cough source and blocked 68 percent of small particle aerosols, Al Mohajer noted. [JAMA 2020;324:1348-1349; J Occup Environ Hyg 2014;11:509-518]

Indeed, the intervention resulted a significant decline in the predicted proportion of HCPs contracting SARS-CoV-2 (18.0 percent to 3.7 percent; p<0.001) and HAIs (from 8.4 to 1.7 per 1,000 patient-days; p<0.001). “Similar results were described in community health workers in India after implementation of face shields,” he said. [JAMA 2020;324:1348-1349]

“Our findings support universal face shield use as a part of a multifaceted approach in areas of high SARS-CoV-2 community transmission,” according to Al Mohajer.

Face shields are easy to manufacture, which makes them widely available and cheap, he added. They can be washed and disinfected and reused indefinitely.