USC Student Health is conducting a study to estimate the percent of students that have developed COVID-19 antibodies, Chief Health Officer Sarah Van Orman announced in an email Wednesday to USC senior vice presidents, deans and student government.

The university may use the study result to prepare for the physical re-opening of the university campus.

“Participants will be contacted by email shortly from a randomized sample of current USC students residing on or near the University Park Campus,” the email stated. “This study may help us learn more about infection rates of COVID-19 on the USC campus and among USC students and help the university prepare for the physical re-opening of the USC University Park Campus.”

This seroprevalence study closes on or prior to May 8, 2020.

In a Zoom press briefing, Van Orman said that about 500 to 800 USC students living in the Los Angeles area, on or near campus, would receive an email invitation to participate in a COVID-19 antibody test. Selected students who want to participate should visit the Engemann Student Health Center and complete a blood drawing for testing, according to Van Orman. Participants will also receive a copy of their results.

The student participants were randomly selected and is based on recruiting a pool that closely represents the demographics of the campus-based student population overall, but they must be at least 18 years old, Van Orman said. There will be no cost for the testing. Participants will be asked to complete a survey with questions about their previous symptoms, travel, exposure to others during the spring semester, she added. According to the FAQs: USC Student Health’s Seroprevalence Study page on the university website, the study is not open to self-selection, so students who are not selected can not volunteer for the study.

Van Orman said this study would reveal a little bit about how many people may have had it already during the spring semester.

“We know that during the spring, we had a significant number of students tested positive for infection, and we also know that within young adults in particular, infections appear to be asymptomatic or minimally symptomatic....We had a lot of students coming back to campus in January from parts of the world where there was COVID-19. We know that there were students coming back in March from study abroad where there was a lot of COVID-19,” Van Orman said. “So we want to understand what’s an estimate of how many students may have been already infected with the virus.”

Van Orman said the team is trying to get all the specimens collected in about two weeks, and the results are expected to come out within one or two weeks after collecting the specimens.

Data from the study will be analyzed to help the university plan for the next fall, Van Orman said. She said that the result would not determine the actual reopening of the campus; instead, it might help the university to determine how the school reopens.

“For example, if we have a certain group of students that have really high levels of seroprevalence [of the antibody], we might say ‘before you come back to school, we might be able to recommend that those people get tested, for example, for antibodies,’” Van Orman explained. “So if very few people have it, then we’re going to say chances are very low people have the antibodies.”

In the Wednesday email, Van Orman said that antibodies indicate a marker of exposure.

“Currently, the science of antibody is in development. It is not yet clear if and what level of antibodies provide protection against future infections with COVID-19. It is also not known if every person infected with COVID-19 produces antibodies,” she wrote. “Until such questions are answered, antibody testing is best used to estimate previous prevalence of exposure to the virus in a population rather than to guide individual health decisions.”

In the press briefing, Van Orman said that health officials are not sure the meaning of antibodies besides previous exposure.

“Many people are hopeful that over time the COVID-19 antibody will mean that someone might be immune to reinfection. We don’t know that yet,” she said.

On April 10, USC Price School of Public Policy and LA County Department of Public Health conducted a first-of-its-kind COVID-19 antibody test for 1,000 selected LA residents. A preliminary result, which was released April 20 and hasn’t been peer-reviewed yet, revealed that approximately 4.1% of adult residents in Los Angeles County have the antibody to the coronavirus.

On April 22, the World Health Organization warned against the idea of treating the COVID-19 antibody as an “immunity passport” or “risk-free certificate."

“There is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection,” WHO stated in a scientific brief.

According to Harvard Medical School, serologic tests or antibody tests are not sensitive enough to accurately diagnose an active COVID-19 infection, even in people with symptoms, because a person’s body takes at least five to 10 days after they have acquired the infection to develop antibodies to the virus.

Countries like China, Korea and Germany have been conducting widespread testing of asymptomatic individuals for COVID-19, which is different from antibody testing. Antibody testing reveals whether a person had exposure to the virus or past infections, while widespread testing of asymptomatic people is to detect who are silent virus carriers. Van Orman said the USC Student Health is “actively evaluating” the widespread testing or asymptomatic testing.

“We are actively evaluating that particularly for fall about whether that will be helpful as students come back to campus. We just don’t know enough right now,” she said. “We’re fortunate now that we have the ability to test pretty widely people who have any kind of symptoms or who are exposed. But asymptomatic testing is a more complicated issue. It’s not really testing. It falls into what we call screening.”

Los Angeles Mayor Eric Garcetti announced Wednesday afternoon that L.A. becomes the first major city in America to offer free COVID-19 testing to all residents, including those without symptoms.

“The City of Los Angeles, in partnership with the County of Los Angeles and CORE (Community Organized Relief Effort), is providing free COVID-19 testing to ALL Los Angeles County residents, whether or not you are experiencing COVID-19 symptoms,” the L.A. City and L.A. County COVID-19 testing appointment website stated.

According to Garcetti and the testing website, priority for the same or next day testing is still given to people with respiratory symptoms and critical front-line workers who interact with the public while working.

As of April 28, Los Angeles County reported 22,485 confirmed cases of COVID-19 and 1,056 deaths.

On April 27, the Centers for Disease Control and Prevention added six symptoms of COVID-19-chills, repeated shaking with chills, muscle pain, headache, sore throat and new loss of taste or smell-to its list, which had three: shortness of breath, cough and fever. According to the CDC, symptoms may appear with two to 14 days after exposure to the virus.

Update 7:20 p.m., April 29: This story has been updated with L.A. Mayor Eric Garcetti’s announcement on COVID-19 testing.