Becker's Clinical Quality & Infection Control

8 INFECTION CONTROL Antibody tests don't offer strong insights on immunity, infectious disease experts warn By Mackenzie Bean H eightened discussions about the need for COVID-19 booster shots may be driving an uptick in anti- body test requests at some hospitals, though experts say the test results are not a helpful indicator of immunity status, according to an Oct. 1 report from Pew Charitable Trusts. e FDA, CDC and Infectious Disease So- ciety of America do not recommend using antibody tests to determine immunity levels against COVID-19. at's because scientists are still unclear about the level of antibodies needed to offer protection against the virus. "Doctors are ordering antibody tests for peo- ple who are worried about waning immunity, but I see that as problematic," Alan Wells, MD, director of clinical labs at the University of Pittsburgh (Pa.) Medical Center told Pew. "For a normal person, knowing your level eight months later [aer their initial vaccina- tion dosages] is of relatively little value." Dr. Wells said his hospital — like others — saw a jump in requests for antibody testing this fall. He's recommended colleagues use the tests judiciously. Mary Hopkins, MD, associate program director of the infectious disease fellowship program at Tus Medical Center in Boston, said she finds antibody tests useful for pa- tients suspected of having long COVID-19 who never got a PCR test to confirm they had the virus. Antibody tests can also be helpful to determine whether some pop- ulations, such as nursing home residents, developed antibodies aer vaccination. n COVID-19 most contagious in the few days near symptom onset, study suggests By Erica Carbajal C OVID-19 may be most infectious in the two days before and three days after symptom onset while patients are mildly or moderately ill, according to research published Aug. 23 in JAMA Internal Medicine. The study, led by researchers from the University of Georgia in Athens, involved 730 COVID-19 index patients who were diagnosed between Jan. 8 and July 30, 2020, in Zhejiang Province, China, as well as 8,852 of their close contacts. Close contacts were followed through August. Almost 4 percent of close contacts later tested positive. Most were mild or moderate cases, while 18.7 percent were asymptomatic. Close contacts were at highest risk of contracting COVID-19 if they were exposed to an in- dex patient in the two days before and three days after symptom onset, peaking at day zero, findings showed. Additionally, researchers found an association between the index patient and close contact's disease severity. For example, contacts who were exposed to an index patient with a mild or moderate COVID-19 case were more likely to contract the virus compared to those who were exposed to asymptomatic index patients. Close contacts who tested positive were more likely to be as- ymptomatic if the index patient was also asymptomatic. "Infected contacts of asymptomatic index patients were less likely to present with COVID-19 symptoms, suggesting that quantity of exposure may be asso- ciated with clinical presentation in close contacts," researchers said. n How an immediate boost in vaccination rates could affect COVID-19 hospitalizations, deaths By Erica Carbajal A simulation model involving 10 states predicted 19,500 fewer hospitalizations and 6,900 fewer deaths from COVID-19, assuming daily vaccination rates increased by 50 percent in the last week of August 2021 and continued through March 2022. About 344,341 total cases were averted in the model, according to the Oct. 5 analysis from The Commonwealth Fund. The simulation model involved five southern states in a declining trend that hit their peak number of cases in early September (Alabama, Florida, Georgia, Louisiana and Texas), and five northern states with cases trending upward at the end of September (Michigan, New Hampshire, New York, Pennsylvania and Wisconsin). Researchers used a previously developed COVID-19 transmis- sion dynamics simulation model to forecast what would happen over the next six months if each state accelerated their number of vaccine doses administered by 50 percent above their rate in the last week of August. They compared this to a status quo scenario in which vaccinations continued at the August pace. The estimated number of hospitalizations potentially pre- vented by the end of March 2022 ranges from 65 in New Hampshire to 5,056 in Texas. As far as the number of deaths potentially averted, estimates range from 10 in New Hamp- shire to 1,441 in Florida. Researchers noted that while the model is based on a scenario in which vaccination rates accelerated in August, the findings indi- cate a significant number of cases, hospitalizations and deaths can still be prevented if vaccination rates increased immediately. n

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