The main objective of this study was to estimate the extent of the preexisting seroreactivity against SARS-CoV-2 in the general adult population and its relationship to circulating coronaviruses. To confirm that SARS-CoV-2 antibody reactivity in uninfected adults was genuinely cross-reactive and not due to widespread unreported, asymptomatic SARS-CoV-2 circulation, we similarly assayed sera collected prior to the emergence of SARS-CoV-2 and from infants before and after maternal antibodies have waned. In addition, we used a SPOT peptide array to map this antibody reactivity on the SARS-CoV-2 proteome.
The paper's abstract states:
Preexisting cross-reactivity to SARS-CoV-2 occurs in the absence of prior viral exposure. However, this has been difficult to quantify at the population level due to a lack of reliably defined seroreactivity thresholds. Using an orthogonal antibody testing approach, we estimated that about 0.6% of nontriaged adults from the greater Vancouver, Canada, area between May 17 and June 19, 2020, showed clear evidence of a prior SARS-CoV-2 infection, after adjusting for false-positive and false-negative test results.
Whereby they conclude:
We conclude that most adults display preexisting antibody cross-reactivity against SARS-CoV-2, which further supports investigation of how this may impact the clinical severity of COVID-19 or SARS-CoV-2 vaccine responses.