The WHO IS is a pool of eleven human plasma from convalescent patients and was established in December 2020 by the WHO Expert Committee on Biological Standardization with an arbitrary assigned unitage of 1000 International Unit per mL (IU/mL) for neutralization activity, the role of the IS in binding antibody assays was discussed.
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Improvements in antibody assay comparability are anticipated with the recent introduction of the WHO first International Standard (IS) for anti-SARS-CoV-2 immunoglobulin (NIBSC code 20/136), with the aim of harmonizing immune response assessment after natural infection or vaccination. The Centers for Disease Control and Prevention (CDC) recently highlighted the need for standardized SARS-CoV-2 quantitative IgG and neutralization assays. However, current anti-S protein assays are highly variable in clinical practice according to the different neutralizing activities, possibly due to a lack of reference materials.
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Although this new role has not yet been fully validated scientifically, as we do not know how long persisting antibodies confer protection, it is increasingly clear that antibody assays are needed to monitor and check responses to vaccines to support the interpretation of the clinical outcomes.įor this purpose, standardized anti-SARS-CoV-2 quantitative and neutralizing assays are pivotal in assessing immune responses to vaccines, and it will become essential if a correlation of protection level could be identified with an antibody titre.Īmong the serological assays, those targeting the spike protein, against the Receptor Binding Domain (RBD), the Subunit 1 (S1) or the full Spike (S), have played an important role in vaccine campaigns. highlighted the utility of antibody assays as a highly cost-effective tool for a vaccination strategy to promote public health.
Regarding vaccine application, Gudbjartsson et al. Nowadays, antibody testing may provide valuable data on: 1) surveillance and epidemiological assessment to evaluate the immunization status of the population, 2) diagnosis of suspected cases with negative viral RNA test to increased diagnostic sensitivity for COVID‐19 patients, , 3) selection of hyperimmune plasma for convalescent plasma therapy, 4) therapeutic antibody development and evaluation, 5) assessment of COVID-19 vaccines immune responses and durability. Simultaneously, in September 2020 the WHO issued the target product profiles for COVID-19 diagnostics, indicating 95–97% and 98–99% as acceptable criteria for sensitivity and specificity, respectively. Īs of 12 April 2021, there are at least 655 immunoassays for antibodies that are either commercially available or in development, according to the Foundation for Innovative New Diagnostics (FIND) ( ), a World Health Organization (WHO) collaborating center for Laboratory Strengthening and Diagnostic Technology Evaluation. Since the beginning, the US Food and Drug Administration (FDA) has issued Emergency Use Authorizations (EUA) for hundreds of serological assays to support COVID-19 diagnosis.
SARS-CoV-2 antibody assays have been and continue to be essential in managing the COVID-19 pandemic,.
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