Fig. 4: Comparison of viral loads according to vaccination status, SARS-CoV-2 lineage and clinical symptom status.
a, Grouped box-and-whisker plots and swarm plots showing the differences in mean cycle threshold (Ct) values and calculated viral loads in copies per ml (cp ml−1) between fully vaccinated and unvaccinated cases overall (left) and stratified by lineage (right). For all comparisons, the difference in viral loads was not statistically significant (P > 0.05). For the lineage plots on the right, the mean Ct values and approximate viral loads corresponding to unvaccinated and fully vaccinated cases are shown as μunvaccinated | μvaccinated and cp/mlunvaccinated | cp/mlvaccinated, respectively, below the name. b, Box-and-whisker and swarm plots showing the differences in viral loads between symptomatic and asymptomatic cases, stratified by vaccination status. c, Box-and-whisker and swarm plots showing the differences in viral load between specific lineages identified as VOC/VOI and other lineages that were not designated VOCs or VOIs at the time of this study (‘non-VOC/VOI’). Identified VOCs/VOIs included Alpha, Beta, Gamma, Delta, Epsilon and Iota variants, following the World Health Organization (WHO) nomenclature scheme. d, Box-and-whisker and swarm plots showing differences in viral loads between each VOC/VOI and non-VOC/VOI. For all box-and-whisker plots, the box outlines denote the interquartile range (IQR), the solid line inside the box denotes the median, the dashed line inside the box denotes the mean (μ) Ct value, and the whiskers outside the box extend to the minimum and maximum fold enrichment points. Welch’s t-test was used for significance testing. A standard curve was used to determine the estimated viral load for a corresponding Ct value (Extended Data Fig. 4).
