Most USC students were still vulnerable to COVID-19 in May, antibody study shows

October 15, 2020

A positive test was most associated with loss of smell and taste, not respiratory symptoms

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In the early days of the pandemic, USC student health physicians wanted to find out what percentage of USC’s student body already had been exposed to the coronavirus and carried potentially protective antibodies.

To learn the answer, USC Student Health researchers conducted a student antibody testing study in May that showed just 4% — 31 students out of nearly 800 who answered a questionnaire about risk factors and gave a blood sample — had COVID-19 antibodies, a sign of prior infection.

The rate, which then roughly resembled the rate among L.A. County’s general population, meant that the vast majority of students remained vulnerable to COVID-19.

The results of the USC Student Health study appeared Oct. 15, 2020, in the Journal of Adolescent Health.

Participants were invited to be part of the study via an email invitation that was sent to 9,135 students enrolled for the spring 2020 semester. Only students still living in the area could participate, as they had to come to the student health center for a blood draw.

The study indicates that the virus was not widely circulating in the student population prior to the closure of the physical campus in mid-March 2020. Low levels of virus in L.A., USC’s transition to online learning and California’s statewide shutdown — rather than widespread immunity — kept infection numbers low, researchers believe.

“If we had a large proportion of students showing antibodies, indicating that the virus was widely circulating in our community between January and April, this could have informed our safety plans. But the rate was low,” said lead author Kimberly Tilley, co-director of USC Student Health and a clinical assistant professor of family medicine at the Keck School of Medicine of USC.

Tilley stressed that the prevalence rates are specific to USC and may not be generalized to other institutions of higher learning. Since mid-March, USC has continued to conduct classes in a virtual format.

One surprising takeaway from the study could help USC Student Health doctors zero in on possible COVID-19 cases during cold and flu season. Eighty-one percent of students who tested positive for antibodies reported losing their sense of smell or taste — a symptom associated with the new coronavirus but not influenza.

It is still unclear how much protection antibodies offer.

“Even if antibodies offer some protection – which we don’t know for sure,” said Vladimir Ayvazyan, an assistant professor of clinical family medicine at the Keck School of Medicine and one of the study’s authors. “We believe that the successful reopening of universities will rest on the ability to mitigate spread through physical distancing, environmental measures, promotion of behaviors that reduce spread, contact tracing and access to testing for active infections.”

In addition to Tilley and Ayvazyan, the other authors of the study are Sarah Van Orman, W. James Gauderman, David Conti, Maurice O’Gorman, Eric Kawaguchi, Neha Nanda and Lauren Martinez, all of USC.

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