LOS ANGELES (CBSLA) – While a new round of antibody testing appeared to indicate that Los Angeles County has done a good job limiting the spread of the coronavirus, it also showed that the region is still not close to achieving herd immunity even as the number of coronavirus cases countywide crossed the 40,000-mark Wednesday.
There were 1,324 new L.A. County coronavirus cases and 57 deaths reported Wednesday. It brings the total number of cases to 40,857, and the death toll to 1,970.
Officials also Tuesday released the results from the second phase of an ongoing antibody study being conducted by USC and the L.A. County Department of Public Health.
1,014 Angelenos were tested from May 8-12 in a drive-thru and in-home format. 2.1% of them tested positive for coronavirus antibodies, officials announced.
This was significantly down from the 4.65% who tested positive in the first phase of testing, which was conducted April 10-14, the results of which were published Monday in the Journal of the American Medical Association.
"If you pooled the results across the two waves...about three percent tested positive," lead investigator Dr. Neeraj Sood, a USC professor of public policy, told reporters at a news briefing Wednesday. "Which means we are still far away from herd immunity, and we need to be conscience of that."
Herd immunity occurs when at least 60 percent of a population has been infected with a disease.
Officials speculated that the significant decrease in the number of participants with COVID-19 antibodies between the first and second phases could have been due to a variety of factors. Sood said that antibody levels may have decreased among those who contracted coronavirus early on in the pandemic.
"The amount of antibodies, especially of people who were infected early on, might be waning over time, and our test might not be able to detect these lower levels of antibodies," Sood said.
The second phase was conducted at a completely different site than the first phase. There was also more of an effort made to ensure Latinos, Asians and African-Americans took part in the second phase, L.A. County Public Heath Director Dr. Barbara Ferrer disclosed.
However, officials said that the fact that there was not a significant jump in the number of people with COVID-19 antibodies likely means that the stay-at-home orders are working.
"Despite the limitations, the results suggest there was not much spread of the virus in the general community population during the time between these two surveys," Ferrer said. "And I think this is likely due because so many of us did a great job staying at home, physically distancing and wearing our cloth-faced coverings."
Meanwhile, Ferrer reported that there continues to be a steady decrease in COVID-19 hospitalizations. 1,531 coronavirus patients are currently hospitalized across the county, with 28 percent in ICUs and 19 percent on ventilators.
"And each day we continue to see a slight decrease in the number of people who are hospitalized, and this is good news," she said.
1,033 residents at L.A. County's institutional settings have died of coronavirus, the vast majority of which lived in nursing homes. That accounts for 52 percent of all coronavirus deaths.
Institutional settings include nursing homes, assisted living facilities, jails, prisons, homeless shelters, treatment centers, supportive living facilities, workplaces, restaurants, retailers and educational facilities.
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