WHO International Standard for evaluation of the antibody response to COVID-19 vaccines: call for urgent action by the scientific community

Abstract

The first WHO International Standard and International Reference Panel for anti-SARS-CoV-2 immunoglobulin were established by the WHO Expert Committee on Biological Standardization in December, 2020. The WHO International Antibody Standards are intended to serve as global reference reagents, against which national reference preparations or secondary standards can be calibrated. Calibration will facilitate comparison of results of assays (eg, of the neutralising antibody response to candidate COVID-19 vaccines) conducted in different countries. Use of these standards is expected to contribute to better understanding of the immune response, and particularly of the correlates of protection. This Personal View provides some technical details of the WHO Antibody Standards for SARS-CoV-2, focusing specifically on the use of these standards for the evaluation of the immune response to COVID-19 vaccines, rather than other applications (eg, diagnostic or therapeutic). The explanation with regard to why rapid adoption of the standards is crucial is also included, as well as how funders, journals, regulators, and ethics committees could drive adoption in the interest of public health.

Figure 1

Distribution of the WHO International Standard for anti-SARS-CoV-2 immunoglobulin The map shows the geographical distribution of end users who have acquired the WHO International Standard (National Institute for Biological Standards and Control code 20/136) from December, 2020, until July, 2021. The size of the circle corresponds to the relative number of units shipped per country. The location of the circle within a country is arbitrary and is not pinned to the end user. Overall, more than 2400 units were shipped to 581 individual customers in 46 different countries worldwide.

Figure 2

Harmonisation of live SARS-CoV-2 neutralisation assay results by the WHO International Standard (A) NT₅₀ reported by participants.(B) Antibody potencies expressed as relative to the International Standard, 20/136 in IU/mL. The interquartile range of the values for each sample is represented as a box; the black line within the box marks the median; the bounds indicate minimum (lower bar) and maximum (upper bar) values. Further details on the codes for the WHO reference panel are published elsewhere. IU=International Units. NT₅₀=50% neutralisation titre.