Do face shields provide protection on top of masks? Evidence from this study in India suggest face shields may protect health care workers who interact with #COVID19 contacts, providing more data on #NonPharmaceuticalInterventions for preventing #SARSCoV2 transmission.

In @jama_current, Bhaskar & Arun compared the #SARSCoV2 infection rate before (May 3-15) and after (May 20-June 30) implementing the use of face shields for health care workers (HCW) conducting house visits for asymptomatic contacts in Chennai, India.
https://bit.ly/32ts84U 

Prior to implementing face shields, 62 HCW visited 5,880 households (31,164 people); 12 tested positive for #SARSCoV2 (8 with #COVID19 symptoms). After face shields, 50 HCW visited 18,228 households (118,428 people) and none tested positive.

Strengths: HCW had few other sources of exposure. No changes to protocols between the two periods were noted other than the addition of face shields. HCW had considerable exposure due to visiting many houses and many household contacts subsequently testing positive.

Limitations: The before-after comparison makes it difficult to be certain that other factors did not contribute to the reduction in transmission to health care workers, such as changes in HCW behaviors and precautions among workers that were not measured.

Summary: While other changes in behavior over time may have affected the results, these findings suggest face shields reduced #transmission of #SARSCoV2 from asymptomatic contacts to healthcare workers. https://jamanetwork.com/journals/jama/fullarticle/2769693