Population Health Study to Estimate Prevalence of COVID-19 in CA

May 18, 2020 - The University of California, Irvine, and the Orange County Health Care Agency are partnering to conduct a large-scale population health study that will help researchers determine the true prevalence of COVID-19 in Orange County.

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Researchers are almost certain that the number of COVID-19 cases in the US have been significantly undercounted, since individuals with few to no symptoms are rarely tested.

With a population of 3.2 million, Orange County is the sixth-largest county in the US. Using a representative sample of 5,000 Orange County residents, researchers will conduct serological testing to determine if these people have COVID-19 antibodies.

The results will help public health officials as they reduce social distancing requirements and begin to reopen the economy, while also allowing them to identify at-risk populations and understand how long immunity to the virus lasts.

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“Testing that is scientifically and statistically sound is absolutely critical to getting people all over Orange County back to work and back to their lives in a safe way,” said Bernadette Boden-Albala, director of UCI’s Program in Public Health and founding dean of the campus’s proposed School of Population Health.

“What we’ve seen so far is that low-income and minority communities are experiencing the most severe symptoms and death rates. It’s tragic, and we have to know why this is happening and what we can do to prevent it. By partnering across Orange County, from Irvine and Newport Beach to Santa Ana and Anaheim, we can do this.”

The 5,000 Orange County residents selected for the study will be asked to visit one of eight to ten drive-thru testing sites, where medical personnel will use a simple pinprick to collect blood samples that will be taken to UCI and analyzed for COVID-19 antibodies.

Researchers will compare the results to those of a subset of 200 people who report a positive COVID-19 diagnosis or who test positive. Medical personnel will test this smaller cohort every two weeks for four months so that researchers can see how immune response changes over time and which groups are most at risk.

“We are pleased to partner with a respected academic and research institution like the University of California, Irvine in support of scientific serology studies that may help us understand how much of the population has been infected and who may be eligible to donate plasma to help COVID-19 patients on the path to wellness,” said Dr. Clayton Chau, director of the Orange County Health Care Agency.

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The true rate of COVID-19 is unknown because it’s impossible to determine the actual number of infections without widespread testing of a representative sample. Recent surveys in other metropolitan areas of the US indicate that infection rates are much higher and death rates are lower than previously thought, and that rates vary significantly from place to place.

Testing has shown antibody levels ranging from 2.8 percent in Santa Clara County to 21.6 percent in New York City to 4.1 percent in Los Angeles County. This suggests that the fatality rate could be 28 to 80 times less than currently estimated.

Additional research will be necessary to determine what level of antibodies is enough to confer near- or long-term immunity on those who have had COVID-19. Researchers will soon recruit study participants, with testing expected to take place in June. The team will issue an initial report this summer, and another report is planned to be released in early fall.

In a separate smaller study, UCI researchers are using a $60,000 grant from a COVID-19-related university research fund to examine 1,500 blood samples that will be collected at ten clinics around Orange County.

Researchers chose sites that will enable accurate, diverse representation of the local population, although the sample will be inherently limited to people who visit clinics. This smaller study will provide officials a quick read on COVID-19 exposure rates, but the results won’t be as exact as those from the larger study.

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With this research, UCI expects to shed light on the prevalence of COVID-19, as well as the particular patient populations the virus is affecting.

“COVID-19 is very much a local affair. Different populations are affected differently. Why did Orange County not see the type of spike in cases that afflicted New York?” Boden-Albala said.

“Given the data that has come out of Santa Clara and Los Angeles, and even New York, we need to understand how many people in Orange County have immunity. And that means knowing how many people have been exposed. It would be a hugely different picture if 50 percent of a population were immune compared to 5 percent. The public health response would vary in so many ways.”