Second round of Co-Immunity Project shows high prevalence of infection in west Louisville

Results from the ongoing Co-Immunity Project at the University of Louisville’s Christina Lee Brown Envirome Institute show high levels of coronavirus infections in Metro Louisville. These results confirm previous findings, indicating that 30,000 to 40,000 people may have been exposed to the virus in Jefferson County since the beginning of the pandemic and that the rate of infection is higher in west Louisville than in other neighborhoods.

The Co-Immunity Project is a unique series of studies to estimate the true prevalence of SARS-CoV-2, the virus causing COVID-19, in Jefferson County by testing a representative sample of individuals from different areas in the city in proportion to the age and race of the population of the area every eight weeks. The approach adopted by study investigators provides a more reliable estimate of the spread of coronavirus infection in different parts of the city than simply testing whoever comes forward to be tested.

The random sampling of different neighborhoods also allows the team to identify areas with high prevalence of infection. Their results show that the rate of infection is 10 to 12 percent in western Jefferson County but 2 to 4 percent in other parts of the county.

In the most recent effort to obtain a uniform sample of city residents, investigators at the UofL Brown Envirome Institute mailed 32,000 letters to households across the city. They followed up the invitation letters with post card reminders, some delivered to the doors of invitees in person.

Between Sept. 9 and 19, the team tested 2,208 individuals at seven different community drive-up locations for both the presence of the virus in participants’ nasal swabs and for antibodies against the virus in their blood, indicating a previous infection. Samples were analyzed at UofL’s Regional Biocontainment Laboratory (RBL) by the Center for Predictive Medicine for Biodefense and Emerging Infectious Disease (CPM).

Invitations were sent to individuals selected using addresses derived from U.S. Census Bureau tract boundaries. Households provided data on the adults in their household. Using these data, one adult was sampled from each household that responded.

A total of 2,208 individuals were tested, 1,576 in response to the invitations and an additional 632 who booked their own appointments after hearing about the study in the news or on social media.

The researchers are planning to repeat randomized coronavirus testing in Jefferson County in November.

This study was supported in part by the James Graham Brown Foundation, the City of Louisville, the Owsley Brown Family Foundation, Foundation for a Healthy Kentucky and others.