(a) Levels of IgG antibodies to the spike of the infecting strain in sera from donors infected with the D614G or B.1.1.7 strains, over time since onset of symptoms (for symptomatic cases) or the first positive RT-qPCR diagnosis (for asymptomatic cases). Levels are expressed as a percentage of the positive control. (b) Neutralising antibody levels (IC50) against the closest infecting strain (Wuhan for D614G infection and B.1.1.7 for B.1.1.7 infection) in sera from donors infected with the D614G or B.1.1.7 strains, over time since onset of symptoms or since the first positive RT-qPCR diagnosis. (c) Correlation of binding IgG and neutralising antibody levels from a and b, respectively. (d) Comparison of binding IgG, IgM, and IgA antibody levels and of neutralising antibody levels (IC50) between B.1.1.7-infected asymptomatic donors and those with mild COVID-19 symptoms. Antibody binding and virus neutralisation were tested against the homologous B.1.1.7 spike and virus, respectively. Differences between the two groups were not statistically significant. Grey horizontal lines denote the lower and upper limit of detection. In (a-d), each symbol represents an individual sample.