Efficacy of Face Shields: Looking at Infection Rates of SARS-CoV-2 Among Health Workers in India

The coronavirus disease 2019—also known as SARS-CoV-2— has been predominantly believed to be spread and transmitted via respiratory droplets when infected persons come into close contact with uninfected persons. While it’s potentially possible that airborne transmission could play a role in the spread of SARS-CoV-2, the dominant form of transmission is believed to be via respiratory droplets from infected people in close proximity to others.

Because so much has been left unanswered about SARS-CoV-2, it’s advised that one of the best ways to limit exposure and increase protection is to wear face coverings or masks while social distancing. In this same vein, the use of face shields has been proposed to help prevent transmission within communities.

The ideology behind this concept is to prevent infected respiratory droplets from coming into contact with uninfected, however, the data to support the efficacy of face shields is severely lacking.

That being said, a community in Chennai, India, was examined and studied beginning on May 3, 2020, in order to get a better look at the actual efficiency and efficacy of face shields in limiting the spread of SARS-CoV-2.

The Methodology: Examining a Community in India

At the beginning of May 2020, 62 community health workers in India were assigned the jobs of counseling asymptomatic family members of patients who had tested positive for SARS-CoV-2 in their homes.

The health workers were isolated in separate hostel rooms, provided food, and were not permitted to visit their own homes or public settings outside of work. They communicated with other workers via phone and all workers prior to May 1, 2020, had been tested and received negative results for SARS-CoV-2.

Of course, workers were provided with adequate PPE including alcohol rub, 3-layered surgical masks, shoe covers, and gloves. When they met with asymptomatic family members, they maintained proper social distance and most of the family members were counseling (though not all) wore masks.

On May 16, two workers developed SARS-CoV-2 symptoms. The remaining 60 workers were monitored and tested for SARS-CoV-2—between the 16^th-19^th, they were not permitted home visits to the families.

On May 20, the health care workers had face shields made of polyethylene terephthalate added to their PPE arsenal. These masks were decontaminated after each and every visit.

The Results: The Efficacy of Face Shields

Before May 20 when face shields were added to the list of PPE, 62 workers visited 5,880 homes with 31,1164 people. Of those 5,880 homes, 222 people tested positive for SARS-CoV-2 between May 4-May 13.

During this period, 12 workers (roughly 19 percent) were infected. Eight of them developed common symptoms while four of the infected remained asymptomatic.

After face shields were introduced following May 20, 50 of the workers (those who were previously uninfected) kept counseling and visiting 18,228 homes. Among those homes were 118,428 people, of which nearly 2,700 were infected with SARS-CoV-2.

No workers developed asymptomatic or symptomatic infections after the addition of face shields.