Study indicates an association of SARS-CoV-2 seropositive antibody test with risk of future infection

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A cohort study of more than 3.2 million U.S. patients evaluated the comparative risk of severe SARS-CoV-2 infection for individuals who are antibody-positive vs. those who aren’t. The study was conducted to understand the effect of serum antibodies to SARS-CoV-2 on susceptibility to future infection, which they deemed important to identify at-risk populations and possibility of implications for vaccine deployment.

Primary end points were post-index diagnostic nucleic acid amplification test (NAAT results), with infection defined as a positive diagnostic test post-index, measured in 30-day intervals (0-30, 31-60, 61-90, >90 days).

The study concluded:

  • Patients with positive antibody test results (IgG) were initially more likely to have positive NAAT results, consistent with prolonged RNA shedding
  • The positive-antibody patients became markedly less likely to have positive NAAT results over time, suggesting that seropositivity is associated with protection from infection (the duration of protection is unknown, and protection may wane over time).
  • These results indicate that seropositive individuals were more likely to have had symptoms of and/or a diagnosis of COVID-19 than seronegative individuals (although the majority of subjects in both groups lacked evidence of prior infection in the observable data)
  • The degree of protection (10-fold) associated with seropositivity appears to be comparable to that observed in the initial reports of the efficacy of mRNA vaccines in large clinical trials1,2,3
  • Protection induced by a vaccine is clearly preferable, as the population-wide risk of a serious outcome from an authorized or approved vaccine is expected to be orders of magnitude lower than that from natural infection

At a Glance

3257478
Unique patients with an index antibody test
10
The degree of protection (10-fold) associated with seropositivity appears to be comparable to that observed in the initial reports of the efficacy of mRNA vaccines in large clinical trials
11.6 %
Were antibody-positive; while 88.3% were antibody-negative

1Hopkins JS. Pfizer’s Covid-19 vaccine proves 90% effective in latest trials. Wall Street Journal. November 9, 2020. Accessed November 9, 2020. https://www.wsj.com/articles/covid-19-vaccine-from-pfizer-and-biontech-works-better-than-expected-11604922300

2National Institutes of Health. Promising interim results from clinical trial of NIH-Moderna COVID-19 vaccine. November 15, 2020. Accessed December 11, 2020. https://www.nih.gov/news-events/news-releases/promising-interim-results-clinical-trial-nih-moderna-covid-19-vaccine

3Polack FP, Thomas SJ, Kitchin N, et al; C4591001 Clinical Trial Group. Safety and efficacy of the BNT162b2 mRNA Covid-19 vaccine. N Engl J Med. 2020;383(27):2603-2615. doi:10.1056/NEJMoa2034577

Source: Harvey RA, Rassen JA, Kabelac CA, et al. Association of SARS-CoV-2 Seropositive Antibody Test with Risk of Future Infection. JAMA Intern Med. Published online February 24, 2021. doi:10.1001/jamainternmed.2021.0366

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