A just-published study found 253 seemingly healthy Providence employees out of more than 10,019 who tested positive for antibodies to COVID-19.

That is considered a low rate (2.53%) and gives confidence that aggressive social distancing and the use of personal protective equipment such as face masks are effective.

Researchers at the Earle A. Chiles Research Institute at Providence Cancer Institute conducted the testing in late spring. Employees of eight Providence hospitals throughout Oregon lined up for the blood test.

Researchers say the findings highlight the limitations of current testing for COVID-19 antibodies.

“Health care workers were and are an important group to study because we need to know how common exposure is with the people who serve in our medical centers and who otherwise don’t have signs or symptoms of infection,” said Dr. Carlo Bifulco, co-investigator of the antibody research project, and medical director of Providence St. Joseph Health Cancer Genomics Laboratory.