Greater Seattle Coronavirus Assessment Network (SCAN) resumes COVID-19 testing

SCAN is re-launching on Wednesday, June 10th, while upholding the spirit of #ShutDownSTEM. The study’s researchers move forward with their work, including outreach to underserved communities, and recognize the disproportionate impact that COVID-19 is having on Black communities and other people of color, with devastating consequence. Black Lives Matter. The team stands with those across the United States fighting racial injustice.

The greater Seattle Coronavirus Assessment Network (SCAN) will resume testing of home-based, self-collected samples for COVID-19 and return of results on June 10th, 2020.

SCAN will resume operations as a research study with institutional review board (IRB) approval and oversight from the University of Washington, Seattle Children’s, and Fred Hutchinson Cancer Research Center. This follows a pause beginning on May 12th, after the Food & Drug Administration (FDA) clarified their guidance for home-based, self-collected samples to test for COVID-19. SCAN continues to pursue an Emergency Use Authorization (EUA) from the FDA.

As SCAN resumes testing, the study will continue to inform King County’s public health response. Based on learnings from the first phase of the program, the SCAN study will dedicate additional testing resources to previously under-represented groups in south King County, and conduct outreach to encourage greater enrollment within American Indian, Black, Hispanic or Latinx, and Native Hawaiian or Pacific Islander communities.

In this next phase, the study will make more tests available for high-risk groups as well as for family members and close contacts of individuals who test positive. Children 18 years of age and under will also receive priority. Testing in homeless shelters and among healthcare workers in long-term care facilities will continue under the Seattle Flu Study.

“SCAN continues to provide an important and unique window into the COVID-19 outbreak across King County, and in its next phase will also help us expand access to testing for at-risk groups,” said Dr. Jeff Duchin, Health Officer for Public Health – Seattle & King County. “This data can inform public health decisions in the weeks and months to come as King County takes steps to increase activities and get back to work.”

“We still have a lot to learn about how COVID-19 is affecting people who don’t receive medical care, and the insights we gain from SCAN data could help us form a more complete picture of the pandemic,” said Dr. Kathy Lofy, State Health Officer for the Washington State Department of Health. “I’m excited to see SCAN resume operation and continue collecting these important data.”

New SCAN participants are invited to enroll at Please note that daily enrollment is limited.

Has the SCAN program changed under IRB oversight?

SCAN’s sample collection and testing processes, research and analysis capabilities, institutional partnerships, and operational mission to support King County’s public health response remain unchanged.

As part of the shift to a research study under IRB oversight, SCAN participants will complete a longer consent form when signing up, rather than the shorter permissions form that was previously used for the program. A consent form is a required practice in research studies, and outlines more information so that individuals can understand the research study design and agree to participate.

SCAN will also make more tests available to under-represented communities, individuals at higher risk of contracting COVID-19, children under 18 years of age, and family members and close contacts of SCAN participants who test positive for the virus.

Has SCAN received FDA emergency use authorization (EUA)?

SCAN continues to work with the FDA to complete the EUA process. The program initiated the process on March 23rd and has submitted data to validate the safety and reliability of its test, including information on user safety, proper specimen collection, and shipping and specimen stability. As the FDA reviews this information, SCAN is operating in accordance with FDA policy stating that “COVID-19 tests for at-home self-collection may be used as part of an Institutional Review Board (IRB)-approved study.”

Are samples that were collected before the pause still being tested?

SCAN is unfortunately unable to return test results for samples submitted prior to the May 12th pause. Although the Institutional Review Board (IRB) has authorized SCAN to move forward as a research study, allowing for both COVID-19 testing and return-of-results, it is not within the board’s purview to provide retroactive approval for previously submitted samples. The team understands this is frustrating and will contact impacted individuals directly with more information.

It’s important to note that SCAN is a respiratory virus monitoring program and not a clinical service. If you believe you either have COVID-19 or have been in contact with someone who has tested positive for the virus, please stay home, contact your healthcare provider, and follow public health guidance.

Why did SCAN have to pause operations?

The FDA recently clarified its policy for home-based, self-collected samples to test for COVID-19. While SCAN’s lab-developed test is authorized by the Washington State Department of Health, the program was notified that separate federal emergency use authorization is required to return results for tests of self-collected specimens. On May 12th the FDA directed SCAN to pause testing until receiving this additional authorization.

The team initiated the process to secure its EUA from the FDA on March 23rd, 2020, and initially submitted data on April 13th to validate the safety and reliability of its sample collection and diagnostic testing. SCAN has continued to share information with the FDA and most recently submitted additional data on May 26th.

The FDA is currently reviewing this data and the team hopes to receive its EUA soon. In the meantime, SCAN has been advised that operating as a research study under IRB oversight is consistent with current FDA policy.

Are there concerns about the safety or accuracy of SCAN’s test?

There are no concerns about the safety or accuracy of SCAN’s test. 

SCAN has validated the safety of the nasal swabs used for self-collection of samples, the shipping stability of home-collected specimens, and the reliability of SCAN’s diagnostic test for detecting SARS-CoV-2 (the virus that causes COVID-19). All SCAN samples are tested in a laboratory certified for clinical testing by the Washington State Department of Health. The validation data SCAN has submitted to the FDA is gathered from testing more than 17,000 home-collected samples through both the Seattle Flu Study and SCAN.

  • Safety
    SCAN’s data demonstrates the safety and usability of its test. Since the program’s original launch as the Seattle Flu Study, only a single, minor adverse event has been reported. A participant noted discomfort and a red face while swabbing, and these symptoms resolved within 10 minutes and did not require medical attention.

  • Usability and Specimen Adequacy
    The design of SCAN’s test makes it easy for participants to self-collect samples in the comfort of their own home. SCAN’s usability studies confirmed that samples collected by program participants had a high rate of “specimen adequacy,” and that most participants felt confident that they had swabbed correctly. Even when participants expressed concerns about having done a poor job of self-swabbing, their samples consistently contained sufficient levels of a human biomarker to return precise test results. Specimen adequacy for SCAN samples is comparable to samples collected in clinical settings.
  • Stability
    SCAN has conducted studies to determine the stability of home-collected specimens, to understand if returning samples to SCAN’s lab by delivery service or mail could affect test results, given transit time or changes in temperature. SCAN’s stability studies showed that SARS-CoV-2 detection remains stable for up to nine days at temperatures as high as 28 degrees Celsius (82 degrees Fahrenheit).
  • Test Accuracy (Sensitivity and Specificity)
    Test sensitivity measures how well a test correctly identifies an infection. Ensuring that tests have high sensitivity is particularly important for COVID-19 because an incorrect negative result has significant public health impacts. To increase its sensitivity, SCAN’s test measures two different regions of the novel coronavirus, and can accurately detect even a low level of COVID-19 viruses in each sample.

Another important test metric is high specificity, which ensures that negative test results truly indicate that an infection is not present, avoiding the risk of returning a false negative result. SCAN’s lab tested more than 300 specimens that were known to be negative for COVID-19 because they were collected prior to the COVID-19 outbreak. None of these specimens had any detectable SARS-CoV-2 with SCAN’s test. The team also confirmed that even specimens known to be positive for other respiratory viruses, such as flu and importantly, seasonal coronaviruses that cause cold-like symptoms, won’t cause its test to return a false positive result for SARS-CoV-2.

To date, SCAN is not aware of having missed any positive or negative results. The program has compared its results for more than 100 participant specimens with tests run by other clinical and public health labs. All have returned the same results.

How is SCAN working to achieve a more representative sample of King County’s population?

The SCAN team will work to solicit feedback and expand partnerships with community-based organizations, agencies, and local groups that serve populations who have been under-represented in the program’s previous testing efforts. As the outbreak response continues, SCAN will explore how it can adapt its outreach to the needs of the groups it serves, help increase access to COVID-19 testing, and better represent King County’s population in SCAN data and findings. Please send a note to if you are interested in supporting this work.

What’s does the most recent SCAN data show?

SCAN has released a new technical report for the period between April 16th and May 9th—just prior to pausing community testing and return of results. Key findings include:

  • COVID-19 prevalence in King County likely peaked in late March and declined rapidly during the first half of April. However, the decline had slowed and further reductions in prevalence were no longer apparent in SCAN data between April 16th – May 9th. SCAN estimates that the prevalence of active infections was between 15 and 46 per 10,000 people in the period of May 4th – 9th.
  • More recent case data indicates that transmission has continued to decline through May, though at a slower pace than observed in early April.
  • SCAN participants in south King County had a higher proportion of positive test results relative to participants in north King County.
  • SCAN participants living in larger households are more likely to test positive for COVID-19.
  • Nearly 40% of SCAN volunteers live with another SCAN participant. When a SCAN participant tested positive for COVID-19, subsequent participants in SCAN from that same household were much more likely to test positive.
  • SCAN has introduced strategies to achieve better representation by age, geographic region, race/ethnicity, income, and primary language. These strategies prioritize child enrollment and enrollment of other underrepresented groups.

The greater Seattle Coronavirus Assessment Network (SCAN) launched on March 23rd with a mission to better understand the spread of COVID-19 in King County and provide actionable data to inform public health decisions.

Between March 23rd and May 9th, 2020, the program tested a total of 12,482 self-collected samples from across King County, uncovering 102 SARS-CoV-2 positive results. Of these 102 cases, 87% of respondents had not sought in-person clinical care before enrolling in SCAN—either because their symptoms were not serious enough to contact a doctor, or because they lacked access to health care services. By providing access to free, safe, and reliable at-home testing, SCAN is uncovering previously undetected cases across King County and which can help break chains of transmission in our community.

SCAN estimates that the prevalence of COVID-19 infections in King County was between 15 and 46 in 10,000 for the most recent data period of May 4th – 9th. This translates to between three and ten thousand active infections. Using SCAN’s data and model, researchers estimate with 98% certainty that prevalence in the county has declined since a peak in late March. However, after declining during the first half of April, prevalence has stalled, or at best is declining much more slowly, having stabilized at around 30 per 10,000 people between April 16th – May 9th.

Transmission modelling utilizing more recent case data indicates that transmission has continued to decline through May, albeit at a slower pace than observed in early April. The model estimates that by May 27th the prevalence of total active infections was between 2 and 33 per 10,000 people, with a best estimate of 16 per 10,000 people. This is largely consistent with findings from public health surveillance based on case reports from the health care system (reported through the Washington Disease Reporting System, WDRS).

Analysis of samples from SCAN volunteers has also illuminated trends in COVID-19 infection across the county. Geography appears to be correlated with higher rates of infection, with respondents in south King County— including Federal Way, Des Moines, Auburn, Maple Valley, and Tukwila—testing positive at a higher percentage based on population relative to Seattle, Redmond, and Kirkland. This broad north-south geographic divide is similarly identified in case reports by Public Health – Seattle & King County.

Additional research is needed to confirm these descriptive patterns, including increased representation from residents in southern parts of King County and among key demographics—American Indian, Black, Hispanic or Latinx, and Native Hawaiian or Pacific Islander. To this end, SCAN’s website, surveys, emails, and test kit materials are now available in English, Spanish, simplified and traditional Chinese, Vietnamese, Somali, Korean, Russian, Amharic, Tigrinya, and Tagalog.

SCAN recently launched a priority code system that facilitates enrollment of children, a group so far underrepresented in SCAN’s data. Going forward, this priority code system will extend to other groups to achieve better representation by age, geographic region, race/ethnicity, income, and primary language relative to the King County population. SCAN is partnering with community-based organizations and local leaders to help enroll members of these underrepresented populations.

SCAN researchers have identified another pattern in the data—participants living in larger households are more likely to test positive for COVID-19. And SCAN is helping to identify these cases. Out of nearly 12,500 enrollees, 39.5% of SCAN participants live with another participant in the program, and thirteen positive cases have been detected by follow-up testing within a household after the return of an initial positive result.

“As more volunteers enroll in SCAN, we are able to draw increasingly helpful insights from the data — including that members of large households appear to face greater risk, as do residents of south King County,” said Dr. Jay Shendure, Scientific Director of the Brotman Baty Institute and SCAN’s lead partner. “The insights we gain from broad-based community testing are highly valuable to inform our public health response as this outbreak continues.”

For more information, please visit Public Health – Seattle & King County’s COVID-19 resource page.

SCAN (the greater Seattle Coronavirus Assessment Network) is a research study conducted by the team behind the Seattle Flu Study, in association with Public Health — Seattle & King County. It is executed by the Brotman Baty Institute, a collaboration between UW Medicine, Fred Hutchinson Cancer Research Center, and Seattle Children’s. SCAN relies on data modeling support from the Institute for Disease Modeling (IDM). It is funded by Gates Ventures (the private office of Bill Gates) and receives technical assistance from the Bill & Melinda Gates Foundation and the Centers for Disease Control and Prevention.

Originally published on June 10, 2020.