Seroprevalence of SARS-CoV-2 in an Asymptomatic US Population

• Rigatti S. et al. undertake serological testing of a large cohort of individuals to establish rates of seropositivity to SARS-CoV-2, extrapolating to generate an estimate of the overall prevalence of SARS-CoV-2 antibodies in the United States of America. The calculated seropositivity in the US was 3.8 times higher than the cumulative number of reported cases by the CDC, suggesting higher rates of exposure to SARS-CoV-2 than those indicated by diagnosed SARS-CoV-2 infections.  

Research Highlights

1.  50,255 adults with a median age of 42 years (IQR: 34-54) were tested, of which 56% were male  

2.  3.13 % of tested individuals were positive for SARS-CoV-2 antibodies  

3. No distinct differences in seropositivity were observed based on history of chronic illness, age or sex  

4. Seropositivity from individuals in the state of New York was significantly higher (17.1%) compared to other areas 

5. The total burden of SARS-CoV-2 infections in the US according to their estimates was 6.98 million, 3.8 times greater than reported cases by the CDC as of June 1 2020 

Impact for COVID-19 research:  

• Minimal, but highlights how the cumulative number of infections is likely significantly higher than the reported number of confirmed cases 

Methodologies: 

• Study Type: Epidemiological  

• Key Techniques: Antibody tests were performed using the Roche Elecsys ‘Anti-SARS-CoV-2’ kit (stated sensitivity of 100% and specificity of 99.8%) 

Limitations: 

• Individuals in this study were all tested as part of the process of buying life insurance, skewing the population tested towards healthier and wealthier individuals than average, introducing a potential bias in the data. The tested population was also skewed to towards young adults. Additionally, the study displayed an imbalanced representation of the US states. Finally, the calculations which they used to estimate seroprevalence across the US are not displayed.