Fig. 2
The correlation between the logarithmic values of anti-spike antibody titres [log (S Ab)] at one and seven months after vaccination. The correlation was positively significant in participants with negative antibody titres for nucleocapsid protein [N Ab (−)] at seven months after vaccination (n = 617, blue circles), but was negatively significant in those with positive antibody titres [N Ab (+)] (n = 19, orange circles)