Figure 1.

Titres of WHO International Standard NIBSC 21/338 measured in 15 labs using WHO BioHub virus isolates and estimated GMTs. (A) Dots in each panel indicate the measured titres of variants (with the colours indicating the variant as shown in the key) by each lab against the International Standard (for multiple repeats, the geometric mean is shown). The grey line indicates the geometric mean titre (GMT) of each of these measurements across all datasets. Up or down arrows, respectively, indicate titres at upper and lower limits of detection. The labels at the bottom of each figure indicate the lab making the measurement (the abbreviations are available in Table S1). Data are grouped according to assay types, which are indicated at the top-left corner for each group (MicroNeut, FRNT, PRNT, or PseudoVirusNeut). Labs labelled as (in-house) or labs using assay type of PseudoVirusNeut have isolated their own viruses for these measurements, whereas all the other measurements were made with virus stocks received from the WHO BioHub (and propagated according to each lab’s specified method, accession numbers 2021-WHO-LS-001, 2021-WHO-LS-003, 2022-WHO-LS-014, 2021-WHO-LS-016, 2022-WHO-LS-028, 2023-WHO-LS-001). (B) Each panel in this figure shows the data in Figure 3 after controlling for titre magnitude fitted by the model. The grey line shows the GMT fitted by the model. The bars indicate the 95% high-density interval (HDI) of the posterior for the GMT. The details of the model are given in the SI section Modelling Assay-wise Effects and GM Titres. The number of repeats performed by each lab is given in Table S1.