Preliminary results of a Northwestern University blood test study conclude 20% of Chicagoans carry the antibodies to the coronavirus.
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"The huge majority of the people we are dealing with by in large didn't have any symptoms at all or, if they did, only mild symptoms," said Dr. Elizabeth McNally, Director of Genetic Medicine at Northwestern School of Medicine.
Northwestern took blood spot samples from residents in 10 Chicago zip codes. Neighborhoods were divided up in pairings with high COVID-19 cases in some and lower cases in others.
"There are different rates of COVID infection diagnoses, but the rate of the infection based on antibody tests didn't differ a lot," said Thomas McDade, PhD-Northwestern University Researcher.
The 20% rate was consistent in every zip code as well as tests being done on Northwestern Medical School workers.
"What we think this means is there is a lot more exposure to this than people are aware of," McNally said.
What researchers don't know is whether the people had enough of the positive virus to pass it on to other people.
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The simple home blood prick test being used for this study is much more sensitive and accurate than commercial antibody tests that were developed months ago using very sick COVID patients.
"It was important to have a test that works for the lower level of antibody that we see in the community," McNally said.
Northwestern is in the process of expanding the study to include all Chicago zip codes, the goal is to have 10,000 participants and keep them in the study long enough to determine how long antibodies last.
McDade said, "The $64,000 dollar question is people who have been exposed that did not lead to clinical case of disease, will they have protection?"
Reachers said understanding antibody protection is key until a vaccine is widely available.