SARS-CoV-2 Antibodies Identified Before Cases Recognized in U.S.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies were identified in individuals before the first cases of infection were recognized, according to a study published online June 15 in Clinical Infectious Diseases.

Keri N. Althoff, Ph.D., M.P.H., from the Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues aimed to identify individuals with SARS-CoV-2 antibodies in the early weeks of the U.S. pandemic among All of Us participants in all 50 U.S. states who provided blood specimens from Jan. 2 to March 18, 2020. Participants were considered seropositive if they tested positive for SARS-CoV-2 immunoglobulin G antibodies with the Abbott or EUROIMMUN assays in a sequential testing algorithm.

The researchers found that the estimated sensitivity and specificity of Abbott were100 and 99.5 percent, respectively, and the estimated sensitivity and specificity of EUROIMMUN were 90.7 and 99.7 percent, respectively. For the sequential testing algorithm used in the study, the net sensitivity and specificity were 90.7 and 100.0 percent, respectively. Overall, nine of the 24,079 study participants with blood specimens from Jan. 2 to March 18, 2020, were seropositive; seven of these were seropositive prior to the first confirmed case in the states of Illinois, Massachusetts, Wisconsin, Pennsylvania, and Mississippi.

"This study contributes to the evidence of low-level circulation of SARS-CoV-2 in many states at the start of the U.S. epidemic," the authors write. "Future pandemic management should carefully consider the impact of epidemiologic links in testing recommendations and reduce testing restrictions as early as possible."