Figure 3.

Kinetics of antibody and T cell responses over time. SARS‐CoV‐2 total antibodies were measured in 174 individuals, (49 in 20–39, 108 in the 40–59 and 17 in ≥60 years age group), at baseline, 4 weeks after the first dose, 6 weeks (2 weeks after the 2nd dose) and at 16 weeks (12 weeks post 2nd dose) after the second dose by ELISA. The decline in antibody responses from 6 to 16 weeks was not statistically significant in any age group (A). ACE2 receptor antibodies were measured by the surrogate virus neutralizing test in 92 individuals (32 in 20–39, 43 in 40–59, and 17 in the ≥60 years age group). The decline in antibody levels from 6 to 16 weeks was significant in 40–59 (p = .0007) and ≥60 (p = .005) age group (B). Ex vivo IFNγ ELISpot responses to the S protein overlapping pool of peptides were measured in 37 individuals, with 10 in the 20–39 age group, 18 in the 40–59 age group and 9 in the ≥60 age group. There was no difference (p = .8) in responses between 6 and 16 weeks (C). Antibodies to the RBD of the WT was measured by the haemagglutination assay test in 92 individuals (32 in 20–39, 43 in 40–59 and 17 in the ≥60 years age group). The decline in antibody levels from 6 to 16 weeks was significant in 20–39 (p < .0001), 40–59 (p < .0001) and ≥60 (p = .0002) age group (D). The lines indicate the mean, and the error bars indicate the standard error of the mean. All tests were two‐tailed. ELISA, enzyme‐linked immunosorbent assay; IFNγ, interferon gamma