Abstract
Serological assays are valuable tools for tracking COVID-19 spread, estimation of herd immunity, and evaluation of vaccine effectiveness. Several reports from Saudi Arabia describe optimized in-house protocols that enable detection of SARS-CoV-2 specific antibodies and measurement of their neutralizing activity. Notably, there were variations in the approaches utilized to develop and validate these immunoassays in term of sample size, validation methodologies, and statistical analyses. The developed enzyme-linked immunoassays (ELISAs) were based on the viral full-length spike (S), S1 subunit, and nucleocapsid (NP), and enabled detection of IgM and/or IgG. ELISAs were evaluated and validated against a microneutralization assay utilizing a local SARS-CoV-2 clinical isolate, FDA-approved commercially available immunoassays, and/or real-time polymerase chain reaction (RT-PCR). Overall, the performance of the described assays was high, reaching up to 100% sensitivity and 98.9% specificity with no cross-reactivity with other coronaviruses. In-house immunoassays, along with commercially available kits, were subsequently applied in a number of sero-epidemiological studies aiming to estimate sero-positivity status among local populations including healthcare workers, COVID-19 patients, non-COVID-19 patients, and healthy blood donors. The reported seroprevalence rates differed widely among these studies, ranging from 0.00% to 32.2%. These variations are probably due to study period, targeted population, sample size, and performance of the immunoassays utilized. Indeed, lack of sero-positive cases were reported among healthy blood donors during the lockdown, while the highest rates were reported when the number of COVID-19 cases peaked in the country, particularly among healthcare workers working in referral hospitals and quarantine sites. In this review, we aim to (1) provide a critical discussion about the developed in-house immunoassays, and (2) summarize key findings of the sero-epidemiological studies and highlight strengths and weaknesses of each study.
Highlights
The World Health Organization (WHO) declared the Coronavirus Disease of 2019 (COVID-19), caused by the novel severe acute respiratory syndrome coronavirus 2 (SARSCoV-2), a pandemic on 11 March 2020 [1,2]
Great effort has been made toward developing serological assays for COVID-19 and conducting sero-epidemiolocal investigations in Saudi Arabia
Local sero-surveillance studies are key to accurately estimate the prevalence of populations that have been infected with SARS-CoV-2, those infected but who remained asymptomatic
Summary
The World Health Organization (WHO) declared the Coronavirus Disease of 2019 (COVID-19), caused by the novel severe acute respiratory syndrome coronavirus 2 (SARSCoV-2), a pandemic on 11 March 2020 [1,2]. In Saudi Arabia, policymakers have been proactive in their response to COVID-19 and initiated control measures even before reporting the country’s first case [5,6] These measures include evacuation of all Saudi citizens from Wuhan, China, suspension of international flights from and to more than 20 COVID-19-hit countries, including China, and suspension of Umrah (a shorter version of Muslim pilgrimage to Makkah) and visit to the Holy Mosque [5,6]. We aim to deliver a balanced evaluation of the in-house immunoassays developed in Saudi Arabia, summarize the key findings of the local COVID-19 sero-epidemiological studies, and highlight the strengths and weaknesses of each study. This critical discussion can be valuable for COVID-19 research and for other infectious diseases
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