MONDAY, Nov. 30, 2020 (HealthDay News) — More than one-quarter of health care personnel who were positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies were seronegative on repeat testing about 60 days later, according to research published in the Nov. 27 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Wesley H. Self, M.D., from the Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues collected serum specimens from a convenience sample of frontline health care personnel at 13 hospitals and tested for antibodies to SARS-CoV-2 during April 3 to June 19, 2020, and about 60 days later. The percentage of individuals with seroreversion (antibody signal-to-threshold ratio >1.0 at baseline and <1.0 at follow-up) was examined.

The researchers found that at baseline, 6.0 percent of 3,248 participants had detectable antibodies to SARS-CoV-2. On repeat testing, 93.6 percent of 156 participants experienced a decline in antibody response, as indicated by a lower signal-to-threshold ratio at follow-up versus baseline; 28.2 percent experienced seroreversion. The likelihood of having antibodies detected at the follow-up test was higher for participants with higher versus lower initial antibody responses.

“These antibody declines might not equate to loss of protective immunity or increased risk for reinfection; this was not assessed in this study,” the authors write. “Cross-sectional seroprevalence studies to evaluate population immunity are likely to underestimate rates of previous infection because antibodies appear to only be detectable for a discrete period of time following infection.”

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