MADISON, Wis. – Early results from a statewide survey suggests that in July 2020, about 1.6% of people in Wisconsin were positive for antibodies to the virus that causes COVID-19.
Antibodies indicate if a person has been infected with COVID-19 in the past, even if they did not experience symptoms.
In June, the Wisconsin Department of Health Services (DHS) partnered with the University of Wisconsin School of Medicine and Public Health’s Survey of the Health of Wisconsin (SHOW) and the Wisconsin Sate Laboratory of Hygiene (WSLH) to launch a surveillance study, the Past Antibody COVID-19 Community Survey. The study tracks the prevalence of past infections of COVID-19 across the state of Wisconsin.
The survey is designed to test a statewide, representative sample of people three times in 2020 to 2021 for COVID-19 antibodies, according to Kristen Malecki, director, SHOW.
Estimates from the 1,056 survey participants, so far, differ by health region in the state. Antibody positivity rates ranged from approximately 2.6% in the southeast to 0.3% in western regions.
“These preliminary study results provide better insight to exposures that may have occurred in the months prior to June and July,” Malecki said.
To reduce exposure risk to other study participants and research staff, anyone with a known exposure to COVID-19 in the last two weeks, or who was experiencing symptoms, was asked not to participate, she said.
The first wave of testing was completed in mid-August. The SHOW and DHS teams are preparing for the second wave starting in October, and a third wave over the winter. The same group of individuals are invited to participate at all three waves, including people who have already been tested in the first wave.
In order to conduct this study, SHOW personnel partner with health departments and local community churches and centers to set up sampling collection sites, Malecki said.
The WSLH provides sample collection, analysis and coordination of results.
It takes as many as four weeks to contact, enroll and complete more than 1,000 participants across the entire state.
An antibody test is different than the SARS-CoV-2 diagnostic antigen test that indicates whether someone currently is infected with the virus. People can generate antibodies after an infection, regardless of whether they experienced any symptoms.
It is important to note that the PACCS survey is ongoing and these results are preliminary, and the final results can be expected in early 2021, Malecki said.
“There is still much to learn about how long antibodies last in the human body after infection and whether they are protective against future infections,” she said.