Becker's Clinical Quality & Infection Control

9 INFECTION CONTROL UCSF estimates it prevented 500 employee infections through vaccination By Kelly Gooch A lthough the University of California-San Francisco reported 183 employees or students testing positive for COVID-19 in July, it estimates hundreds of infections were prevented because of vaccination. UCSF spokesperson Kristen Bole said Aug. 2 those 183 cases were from a population of 35,000 people and were identified through routine testing, screening and contact tracing programs. Most people had mild symptoms or were asymptomatic, she said. Eighty percent of the UCSF infections involved UCSF Health employees, and only two people were exposed in the workplace. e remainder acquired COVID-19 in their community or home, said Ms. Bole. Of the 183 people who tested positive in July, 153 had been vaccinated and 30 had not. Only two individ- uals have required hospitalization — one had been vaccinated, the other had not. "ese results reflect how highly effective the vaccines remain, even aer seven months, in some cases. For perspective, without vaccinations, we would expect to have seen 767 COVID-19 cases during that time, given the current positivity rate among those UCSF individuals who have not been vaccinated," Ms. Bole said. As cases rise amid the spread of the delta variant, Ms. Bole said UCSF is "doubling down on our efforts to protect our staff," including requiring employees and trainees to comply with the University of California's vaccination mandate, with limited exceptions for medical or religious reasons. UCSF has also rein- stated its masking requirement for staff, patients and visitors, as well as at-home quarantines for those who have been exposed to COVID-19. UCSF is not the only San Francisco institution that has seen staff members test positive. At Zuckerberg San Francisco General Hospital and Trauma Center, 55 of the more than 7,000 hospital staff members tested positive as of July 31, said hospital spokesperson Cristina Padilla. e hospital said it did not know of any of the infected staff who had been hospitalized. Ms. Padilla said the infections primarily occurred through community exposure. "ZSFG continues to follow strict infection control measures, in- cluding daily self-screening of staff, requiring masks on campus, and testing of all admitted patients," she said. As of July 30, San Francisco was averaging 176 new COVID-19 cases daily, a tenfold increase since the beginning of June, ac- cording to the city's department of public health. n COVID-19 origins may never be clear, bat scientists say By Mackenzie Bean A ll eyes are on scientists exploring the COVID-19 pan- demic's origin. But bat virus researchers, who are still looking for answers about the 2003 SARS outbreak, say there may never be an answer, The Wall Street Journal reported July 11. The virus that causes severe acute respiratory syndrome emerged in 2002 and killed nearly 800 people globally. Linfa Wang, PhD, director of emerging infectious diseases at the Duke-NUS Medical School in Singapore, was part of a team convened by the World Health Organization to investigate the origin of the virus in 2003. Dr. Wang, a bat virus expert, has spent more than a decade working with researchers in China looking for evidence that the virus spread from bats to humans. "There is still no smoking gun," Dr. Wang told the Journal. "We have never found a bat that is the source of SARS that humans have." Now, Dr. Wang is also helping explore COVID-19's origins. Earlier this year, he helped pen research into horseshoe bats in Thailand, some of which tested positive for coronaviruses similar to SARS-CoV-2. But this is still far from a conclusive finding, the Journal said. "We may never know," said Dr. Wang. "We will keep looking." n Delta may push herd immunity threshold over 80%, experts say By Mackenzie Bean I nfectious disease experts say the percentage of the pop- ulation that needs to be vaccinated against COVID-19 to reach herd immunity could be 80 percent or higher, now that the delta variant is spreading rapidly across the U.S., according to Medscape. The estimated threshold for herd immunity is higher because delta is about two times more transmissible than the original virus. "For delta, those threshold estimates go well over 80 percent and may be approaching 90 percent," Ricardo Franco, MD, an assistant professor of medicine at the University of Ala- bama at Birmingham, said during an Aug. 3 briefing hosted by the Infectious Diseases Society of America. Throughout the pandemic, experts have debated at what threshold herd immunity for COVID-19 will occur — and whether it is even attainable. Initially, the general consensus was that 60 percent to 70 percent of the population need to be vaccinated, according to The New York Times. As of Sept. 14, nearly 54 percent of the U.S. population was fully vaccinated against COVID-19, CDC data shows. n

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