Placer launches COVID-19 infection rate study

Published on Oct. 14, 2020

Placer County this week launched a new study aimed at better understanding the COVID-19 infection rate among county residents. 

Led by Stanford University School of Medicine, study investigators will test blood samples from 2,000 residents for COVID-19 antibodies, which indicate a previous coronavirus infection.

As of Oct. 14, a total of 3,845 county residents have tested positive for SARS-CoV2, the coronavirus that causes COVID-19. But because some of those infected with the coronavirus may not have experienced symptoms or sought testing, the actual infection rate in Placer County is suspected to be higher - between 1.3 - 6% of the total population, according to current Stanford estimates. 

“Knowing how widespread COVID-19 really is in our community would tell us a lot about how close we are to achieving some form of immunity and the true fatality rate from the disease,” said District 2 Supervisor Robert Weygandt, who proposed the study for the board’s consideration. “That’s critical information to guide decisions that best protect the physical, social and economic wellbeing of our communities.” 

Investigators will invite a random but representative sample of residents to participate and mail willing volunteers a finger-stick blood test to complete at home. The results of all positive tests and 10% of negative tests will be rerun using a different type of test, producing results with 99% accuracy.

Stanford researchers will develop an online dashboard detailing their findings on the demographic and geographic prevalence of the virus and present a comprehensive report to the Board of Supervisors on the study’s results and conclusions. The study is expected to take about five months to complete. Stanford Medicine and its principal investigator — Dr. Julie Parsonnet, Professor of Medicine (Infectious Diseases) and of Epidemiology and Population Health — are currently working with Santa Clara and Solano counties on similar COVID-19 antibody studies.