Plastic face shields make masks better

One of the biggest challenges of the COVID-19 pandemic is that we just don’t know what works against the SARS-CoV-2 coronavirus. Most of the scientific studies on pandemic control have focused on the influenza virus, which differs from the coronavirus in many ways. The coronaviruses we know something about – SARS, MERS and two common cold viruses – are very different from each other.

We find ourselves without hard data on what is working. Do we need two meters of social distance or three? What types of face masks are the most effective? We are trying to collect data on these issues at the same time as we are implementing them. So, a little bit of good news, we now have data indicating something that is effective: plastic face shields.

Towards the subcontinent!

The work was carried out in India and builds on a public health program launched as the pandemic spread in that country. Workers at a research network in Chennai agreed to self-isolate, then visit families of those who tested positive for SARS-CoV-2 to explain things like quarantine, the use of masks, social distancing, etc.

Before we get to what happened to these workers, we need to step back and admire these people. They agreed to leave their families behind to live in hotel rooms. They were completely isolated from their friends and peers – meals were delivered to their rooms, and even their means of transportation was a van with a steel separator installed to keep them isolated from their driver. All of their direct contact with humans was with people who may have been infected. While families they visited were urged to wear masks and stay at least six feet from health workers, compliance was inconsistent.

And although they were given gloves, surgical masks and an alcohol-based hand sanitizer, it only took two weeks for the first workers to develop symptoms. The program has been suspended and all workers have been tested for the virus. Of the 62 involved, ten had been infected. Together, they visited 5,880 homes and came into contact with a total of 222 people who eventually tested positive for the virus. Fortunately, their transport partitions worked and none of their drivers were infected.

To restart

When the program was restarted, an additional form of protection was put in place: a clear plastic face shield. Health workers were also given ethanol to clean their masks between home visits. With those measures in place, workers visited an additional 18,228 homes, in which 2,682 people ultimately tested positive for the virus.

There was no infection among the healthcare workers.

It is quite possible that the initial infection increased the workers’ sense of caution when restarting the program. But it is not clear whether behavioral changes could be sustained over 18,000 home visits. So, face shields are probably what provided the critical difference.

The authors of the article describing the results are not sure of the essential contribution. The screen could have diverted air around the face or prevented the face mask from being contaminated. It would also provide some protection for the eyes, which is a known route of infection. So there is still more to learn here. But the results seem sufficient to indicate that people at high risk could benefit from using a face shield.

JAMA, 2020. DOI: 10.1001 / jama.2020.15586 (About DOIs).