Oregon study finds 1% of population has COVID-19 antibodies

In Oregon, 1% of all residents show evidence of having had COVID-19, 10 times higher than the reported rate of infections.

According to a recent study from August 2020, 897 blood specimens collected between May and June from health care facilities around Oregon contained antibodies for Sars-CoV-2, the virus that causes COVID-19 in humans.



No antibodies were found in the blood samples of patients aged 17 years or under, implying the rate of infection increases with age; however, the results from the study are “not necessarily generalizable to the entire state population.”

The study’s results show that a significant portion of Oregon’s population has been exposed to the disease than original diagnostic tests showed. 

Paul Cieslak, M.D., study co-author and OHA Medical Director for Communicable Diseases and Immunizations, said “But these results also tell us that the great majority of Oregonians remain susceptible to this virus.”

Seroprevalence surveys like this, where blood is tested to look for antibodies, is expected to reveal a more accurate picture of COVID-19 infection rates, now including asymptomatic patients.

Cieslak said “Because most of us are still susceptible, we need to keep practicing physical distancing and masking until we have effective vaccines, treatments or other means of mitigating illness.”

One question the study was unable to answer, however, was whether the presence of COVID-19 antibodies meant a person is protected from getting the virus again.

Which is why Cieslak said it’s still best to maintain physical distance from others you have not quarantined with and continue wearing CDC-recommended face coverings.

According to the Center for Disease Control website, antibody testing cannot be used to determine active infections because it typically takes the body 1 to 3 weeks to develop antibodies after an infection.

A positive result for the antibody test also does not necessarily mean a patient had COVID-19.

“A positive test result shows you may have antibodies from an infection with the virus that causes COVID-19,” the website reads, “However, there is a chance a positive result means that you have antibodies from an infection with a virus from the same family of viruses (called coronaviruses), such as the one that causes the common cold.”

It’s currently unknown how long any protection antibodies may give for COVID-19, if any, but scientists are still working to understand this.

If a patient tests negative, though, this does not necessarily mean they have not been infected with COVID-19.

“The test may be negative because it typically takes 1–3 weeks after infection for your body to make antibodies,” the website reads. “It’s possible you could still get sick if you have been exposed to the virus recently. This means you could still spread the virus.”

Some patients may take longer than the typical 1 to 3 weeks to produce antibodies for COVID-19, while other patients may not produce antibodies at all, according to the CDC website.

Despite a positive or negative antibody test, both the study and the CDC conclude social distance practices and face coverings are best practices to prevent further spread and infection.