More invites for Placer COVID-19 infection study to be mailed this week

Published on Feb. 4, 2021

Another 5,000 Placer residents will be invited this week to join Placer County’s COVID-19 infection rate study.

Placer launched the study in October 2020 to better understand the coronavirus infection rate among county residents. 

Led by Stanford University School of Medicine, investigators aim to test blood samples from 2,000 residents for COVID-19 antibodies, which indicate a previous coronavirus infection. A random but representative sample of residents have been invited to participate by completing a finger-stick blood test at home. 

As of a mid-study report presented to the county Board of Supervisors on Jan. 12, Stanford had received 1,240 responses out of 15,000 invitations mailed. This week’s invitations are expected to be the study’s last. 

A total of 18,670 county residents as of Feb. 3 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 was suspected to be higher - between 1.3 - 6% of the total population, according to initial Stanford estimates. 

Stanford researchers will provide detailed demographic and geographic data on the 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 be completed in April.

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.