Differential Dynamics of Humoral and Cell-Mediated Immunity with Three Doses of BNT162b2 SARS-CoV-2 Vaccine in Healthcare Workers in Japan: A Prospective Cohort Study

Abstract

Vaccines against SARS-CoV-2 with good efficacy are now available worldwide. However, gained immunity diminishes over time. Here, we investigate the course of both humoral and cell-mediated immunity in response to three doses of the Pfizer mRNA BNT162b2 SARS-CoV-2 vaccine in healthcare workers in Japan. SARS-CoV-2 anti-receptor-binding domain (RBD) antibodies (total Ig, IgG), neutralizing antibodies (NAb), and ELISpot were measured in serum and whole blood samples collected after each vaccine dose. ELISpot numbers were higher than the cutoff values in most participants at all times. It was suggested that the difference in behavior between humoral immunity and cell-mediated immunity with age is complementary. Anti-RBD total Ig, IgG, and NAb indicated a high correlation at each time point after vaccine doses. Total Ig was retained long-term after the second dose and increased significantly faster by the booster dose than IgG. Nab levels of all subjects were ≤20% six months after the second dose, and the correlation coefficient was greatly reduced. These are due to the avidity of each antibody and differences among commercial kits, which may affect the evaluation of immunokinetics in previous COVID-19 studies. Therefore, it is necessary to harmonize reagents categorized by the same characteristics.

Keywords: BNT162b2 vaccine; ELISpot-; SARS-CoV-2; T-SPOT; anti-RBD antibody; antibody avidity; cell-mediated immunity; harmonize; humoral immunity.

Figure 1

(a–h). A one-year dynamics of humoral and cell-mediated immunity against SARS-CoV-2 with three doses of the BNT162b2 vaccine. The levels of anti-RBD total Ig (a,b) and IgG (c,d), neutralizing antibodies (e,f), and T-SPOT (g,h) against SARS-CoV-2 are plotted in a time series after vaccine dose by gender and age. Blue and red plots represent the results by gender. Green and orange plots represent the results by age in two groups over or under 45 years old. The yellow plots represent the median of each time point in the group. The dashed line represents the cutoff value in each immunity parameter. p-values were calculated using the Mann–Whitney U test, and significance was set at 0.05. The arrow (black) indicates the vaccine dose date (the first, second, and booster doses were injected in March 2021, April 2021, and January 2022, respectively). Y-axis: (a,b), anti-RBD total Ig (Elecsys^® anti-SARS-CoV-2 S; Roche); (c,d), anti-RBD IgG (HISCL^TM SARS-CoV-2 S-IgG; Sysmex); (e,f), neutralizing antibodies (SARS-CoV-2 Neutralization Antibody Detection Kit; MBL); (g,h), T-SPOT (T-SPOT^® Discovery SARS-CoV-2; Oxford Immunotec). The anti-RBD antibodies and T-SPOT are shown on a log scale.

Figure 2

(a–i). Correlation at time points between age and anti-RBD total Ig after BNT162b2 vaccine doses. Parameter levels indicating anti-RBD total Ig of humoral immunity against SARS-CoV-2 are plotted and compared according to age at each time point post-vaccine doses. Time points until one month after two doses are colored blue (a–d), from two months to 10 months after two doses are colored yellow (e–h), and two weeks after the booster dose are colored red (i). p-values were calculated using Spearman’s rank correlation test and significance was set at 0.01. Red values indicate a significant correlation (rs, Spearman’s rank correlation coefficient).

Figure 3

(a–i). Correlation at time points between age and anti-RBD IgG after BNT162b2 vaccine doses. Parameter levels indicating anti-RBD IgG of humoral immunity against SARS-CoV-2 are plotted and compared according to age at each time point post-vaccine doses. Time points until one month after two doses are colored blue (a–d), from two months to 10 months after two doses are colored yellow (e–h), and two weeks after the booster dose are colored red (i). p-values were calculated using Spearman’s rank correlation test and significance was set at 0.01. Red values indicate a significant correlation (rs, Spearman’s rank correlation coefficient).

Figure 4

(a–i). Correlation at time points between age and neutralizing antibodies after BNT162b2 vaccine doses. Parameter levels indicating neutralizing antibodies of humoral immunity against SARS-CoV-2 are plotted and compared according to age at each time point post-vaccine doses. Time points until one month after two doses are colored blue (a–d), from two months to 10 months after two doses are colored yellow (e–h), and two weeks after the booster dose are colored red (i). p-values were calculated using Spearman’s rank correlation test and significance was set at 0.01. Red values indicate a significant correlation (rs, Spearman’s rank correlation coefficient).

Figure 5

(a–j). Correlation at time points between anti-RBD total Ig and IgG after BNT162b2 vaccine doses. The levels of parameters indicating anti-RBD total Ig and IgG of humoral immunity are plotted, and the correlation is compared using all or each time point post-vaccine doses. Antibody titers at all time points are indicated on a log scale (a). Time points until one month after two doses are represented by blue (b–e), from two months to 10 months after two doses are represented by yellow (f–i), and two weeks after the booster dose are represented by red (j). p-values were calculated using Spearman’s rank correlation test, and significance was set at 0.01. Red values indicate a significant correlation (rs, Spearman’s rank correlation coefficient).

Figure 6

(a–j). Correlation at time points between anti-RBD total Ig and neutralizing antibodies after BNT162b2 vaccine doses. The levels of parameters indicating anti-RBD total Ig and neutralizing antibodies of humoral immunity are plotted, and the correlation is compared using all or each time point post-vaccine doses. Antibody titers at all time points are indicated on a log scale (a). Time points until one month after two doses are represented by blue (b–e), from two months to 10 months after two doses are represented by yellow (f–i), and two weeks after the booster dose are represented by red (j). p-values were calculated using Spearman’s rank correlation test, and significance was set at 0.01. Red values indicate a significant correlation (rs, Spearman’s rank correlation coefficient).

Figure 7

(a–j). Correlation at time points between anti-RBD IgG and neutralizing antibody after BNT162b2 vaccine doses. The levels of parameters indicating anti-RBD IgG and neutralizing antibodies of humoral immunity are plotted, and the correlation is compared using all or each time point post-vaccine doses. Antibody titers at all time points are indicated on a log scale (a). Time points until one month after two doses are represented by blue (b–e), from two months to 10 months after two doses are represented by yellow (f–i), and two weeks after the booster dose are represented by red (j). p-values were calculated using Spearman’s rank correlation test, and significance was set at 0.01. Red values indicate a significant correlation (rs, Spearman’s rank correlation coefficient).

Figure 8

(a–f). Correlation at time points between age and T-SPOT after BNT162b2 vaccine doses. Parameter levels indicating T-SPOT of cell-mediated immunity against SARS-CoV-2 are plotted and compared according to age at each time point post-vaccine doses. Time points until two weeks after two doses are colored blue (a,b), from two months to 10 months after two doses are colored yellow (c–e), and two weeks after the booster dose are colored red (f). p-values were calculated using Spearman’s rank correlation test and significance was set at 0.01. Red values indicate a significant correlation (rs, Spearman’s rank correlation coefficient).