Trends in Preventive Measures: An Update on Ancestry’s COVID-19 Research Study
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“We observed that those infected with severe COVID-19, determined by being hospitalized or becoming a critical case, were less likely to report having worn a mask inside within seven days prior to their illness onset, compared to those who weren't hospitalized.”


As we move through another season of the global pandemic, public health research  continues to deepen our understanding of the impact personal protective measures can have on COVID-19 susceptibility and severity. Thanks to more than 750,000 Ancestry customers who volunteered to participate in Ancestry’s COVID-19 Research Study, we are now able to contribute additional insights to help advance this evolving body of knowledge. The CDC recommends using preventive measures to protect ourselves and others from infection. But what about affecting our chances of severe disease? Here we suggest that the use of preventive measures is associated with reduced severity of COVID-19 infection. This opens the important possibility that masks and physical distancing may not only reduce our chances of getting infected but also reduce our chances of a severe infection. 

Wearing Masks Indoors & Reduced COVID-19 Hospitalizations

In April 2020, we launched the AncestryDNA COVID-19 Research Study to look for both genetic and non-genetic clues on how individuals respond to the novel coronavirus that causes COVID-19. With this study we are already learning new information about both susceptibility (why some people are more likely to be infected) and severity (why some people suffer severely and others only mildly) of the disease. Exploring the self-reported de-identified survey responses provided by Ancestry customers from all 50 states in both urban and rural areas, we are also learning more about personal choices around the use of masks and physical distancing. We hope these insights will contribute to the body of knowledge around preventive measures and will be validated by other researchers with clinical information.

We observed that those infected with severe COVID-19, determined by being hospitalized or becoming a critical case, were less likely to report having worn a mask inside within seven days prior to their illness onset, compared to those who weren't hospitalized  (Figure 1). This finding, based on an investigation in over 3,000 people with symptomatic COVID-19, holds true even after accounting for differences in age, biological sex, and comorbidities. This trend, that preventive measures are associated with a less severe outcome, is also observed for those who report having worn masks outside and practiced physical distancing.

Although we are only reporting an association observed in our data and do not have information on viral load for each infected person, we do note that these results are consistent with recent studies about higher viral exposure levels contributing to more severe COVID-19 infections. 1,2. It is also noted that viral aerosol levels are higher indoors than outdoors. 3,4 

Trends in Preventive Practices

Self-reported responses in the study also provide insights into who is wearing masks and when and where they are wearing them. In our data, we find that people in all age groups report wearing a mask while indoors and in public at very high rates (> 94%). Older people are more likely to report wearing a mask outdoors when within six feet of others and to maintain six-foot physical distancing (Figure 2). ​​

We also observed that females are more likely than males to report wearing masks and maintaining six-foot physical distancing (Figure 3).

We also wanted to understand how individuals with pre-existing health conditions make choices around preventive measures. We observe that those with pre-existing conditions are more likely than those with no pre-existing conditions to wear a mask and maintain six-foot physical distancing. Given the nature of our self-reported data, we currently cannot speak to whether this is due to perceived increased risk or other factors (Figure 4). 

We are continually humbled by the outpouring of interest in this study. I’d like to thank each and every one who has participated in this research study because without you, none of this work would be possible.  Thanks to your support, we have contributed to the global scientific community’s body of knowledge, including two scientific preprints:

  1. AncestryDNA COVID-19 Host Genetic Study Identifies Three Novel Loci5
  2. COVID-19 Susceptibility and Severity Risks in a Survey of Over 500,000 People6

At Ancestry, we are dedicated to supporting the health and wellness of our customers and will be providing ongoing updates from our COVID-19 study. 

Kristin Rand, PhD, MPH, Epidemiologist, AncestryDNA


The AncestryDNA COVID-19 Research Team

I’d like to highlight the work of Spencer Knight, Brooke Rhead, Marie Coignet, Milos Pavlovic, Ahna Girshick, and the entire COVID-19 research team. 


The Fine Print 

The AncestryDNA COVID-19 Study provides a highly complete, self-reported dataset that contains information about a multitude of risk factors in the context of COVID-19 susceptibility and severity outcomes. Although we have been collecting data since April 2020, the data for the analysis presented here was collected in the U.S. between July 21 and August 3, 2020. All data in the COVID-19 study has been de-identified by removing direct and indirect identifiers. The results presented here are strictly from self-reported data and are associations, not causal inferences and may reflect differences in social and environmental factors, such as other infection prevention behaviors and healthcare access, between those who report wearing masks and those who do not. This data is about reported preventive behaviors, which we do not verify. The observations by age group (Fig 2) are consistent with the trajectory of evolving trends recently reported by the CDC7.



  1. Ghandi, M. et al. Masks Do More Than Protect Others During COVID-19: Reducing the Inoculum of SARS-CoV-2 to Protect the Wearer. J Gen Intern Med. (2020)
  2. Chan, J. F.-W. et al., Surgical mask partition reduces the risk of non-contact transmission in a golden Syrian hamster model for Coronavirus Disease 2019 (COVID-19). Clin Infect Dis (2020)
  3. U.S. Centers for Disease Control (CDC). Scientific Brief: SARS-CoV-2 and Potential Airborne Transmission (October 5, 2020) Accessed October 26, 2020.
  4. Lelieveld, J. et al., Model Calculations of Aerosol Transmission and Infection Risk of COVID-19 in Indoor Environments. medRxiv (2020)
  5. Roberts, G. H. L., Park, D. S. et al. AncestryDNA COVID-19 Host Genetic Study Identifies Three Novel Loci. medRXiv (2020) 
  6. Knight, S.C., McCurdy, S.R. et al. COVID-19 Susceptibility and Severity Risks in a Survey of Over 500,000 People. medRXiv (2020)
  7. COVID-19 Mitigation Behaviors by Age Group — United States, April–June 2020 (October 27, 2020)