Hello Amen A. A. Bawazir

There could be some points of uncertainty that would need to be addressed.

1. Tests may have imperfect sensitivity and specificity, and studies that do not adjust for test imperfections will produce biased seroprevalence estimates. Complicating this issue is the fact that sensitivity and specificity are, themselves, estimated from data that can lead to statistical confusion if uncertainty is not correctly propagated. For instance, serological assays based on single antigens, while good at diagnosing infected individuals in a clinical setting, may not be ideal in low seroprevalence, population wide Covid-19 screens, where low antibody responses are expected.

2. The population sampled will likely not be a representative random sample, especially in the first rounds of testing, when there is urgency to test using convenience samples and potentially limited serological testing capacity.

3. There is uncertainty inherent to any model-based forecast that uses the empirical estimation of seroprevalence, regardless of the quality of the test, in part because of the uncertain relationship between seropositivity and immunity.

Moreover, just accepting only the presence of specific “neutralizing” antibodies as a surrogate marker of immunological protection against viral infections is not enough in the case of SARS-CoV-2 as it may not provide any benefit from Serosurveillance strategies.

Evidence of spontaneously clearing the symptoms of Covid-19 may be a reliable surrogate marker of individuals' immune competency regardless of its mechanism (namely, antibody-dependent cell cytotoxicity and natural killer cells). Clearance of Covid-19 symptoms is closely followed by clearance of all viable SARS-CoV-2.

Please refer to the article attached below for more information.

Article COVID-19: Way Forward With Serosurveillance Without Overemph...

Best.

Thank you Malcolm for your insights were valuable. However, I would add that the sample size used was adequate to represent healthcare workers who worked in hospitals in two provinces. These included all doctors, nurses, x-ray, physicians, dentists, laboratory personnel, pharmacists, respiratory therapists, nutritionists, auxiliary HCWs such as housekeeping staff, laundry personnel, and social workers.

Regarding the test used, Anti-SARS-CoV-2 was determined with electrochemiluminescence immunoassay (ECLIA) on the cobas, Roche Diagnostics GmbH (Germany). This test provides a qualitative detection of total antibodies (including IgG) to SARS-CoV-2 in human serum and plasma as well as it is certified by WHO and achieved it has a high specificity of 99.81 (CI 95%: 99.6-99.9%) and high specificity of 99.5 (CI 95%: 98.63-99.85%). This test provides a qualitative detection of total antibodies (including IgG) to SARS-CoV-2 in human serum and plasma. Moreover, Results are determined automatically by the software by comparing the electrochemiluminescence signal obtained from the reaction product of the sample with the signal of the cutoff value previously obtained by calibration.

Do you think this evidence will help in clarifying the concept of high seroprevalence of COVID-19 in this population?