BNT162b2 COVID-19 vaccination in children alters cytokine responses to heterologous pathogens and Toll-like receptor agonists

Abstract

Background: Vaccines can have beneficial off-target (heterologous) effects that alter immune responses to, and protect against, unrelated infections. The heterologous effects of COVID-19 vaccines have not been investigated in children.

Aim: To investigate heterologous and specific immunological effects of BNT162b2 COVID-19 vaccination in children.

Methods: A whole blood stimulation assay was used to investigate in vitro cytokine responses to heterologous stimulants (killed pathogens, Toll-like receptor ligands) and SARS-CoV-2 antigens. Samples from 29 children, aged 5-11 years, before and 28 days after a second BNT162b2 vaccination were analysed (V2 + 28). Samples from eight children were analysed six months after BNT162b2 vaccination.

Results: At V2 + 28, interferon-γ and monocyte chemoattractant protein-1 responses to S. aureus, E. coli, L. monocytogenes, BCG vaccine, H. influenzae, hepatitis B antigen, poly(I:C) and R848 stimulations were decreased compared to pre-vaccination. For most of these heterologous stimulants, IL-6, IL-15 and IL-17 responses were also decreased. There were sustained decreases in cytokine responses to viral, but not bacterial, stimulants six months after BNT162b2 vaccination. Cytokine responses to irradiated SARS-CoV-2, and spike glycoprotein subunits (S1 and S2) were increased at V2 + 28 for most cytokines and remained higher than pre-vaccination responses 6 months after BNT162b2 vaccination for irradiated SARS-CoV-2 and S1. There was no correlation between BNT162b2 vaccination-induced anti-SARS-CoV2-receptor binding domain IgG antibody titre at V2 + 28 and cytokine responses.

Conclusions: BNT162b2 vaccination in children alters cytokine responses to heterologous stimulants, particularly one month after vaccination. This study is the first to report the immunological heterologous effects of COVID-19 vaccination in children.

Keywords: BNT162b2; SARS-CoV-2; heterologous; immunisation; innate immunity; mRNA vaccination; off-target effects; paediatric vaccination.

Figure 1

Study CONSORT diagram. The COVID-19-Specific vaccine and heterologous Immunity in MIS BAIR (COSI BAIR) study population is a selection from the BCG for Allergy and Infection Reduction (MIS BAIR) clinical trial. A total of 51 participants were enrolled into COSI BAIR.

Figure 2

Cytokine responses to whole‐blood stimulations 28 days after BNT162b2 vaccination. The mean of the pre (V1) and post (V2 + 28) cytokine differences from 29 study participants is plotted in the heatmap colour gradient, with red representing increases and blue indicating decreases. Each row represents a stimulation condition, and is separated into three groups: bacterial/fungal stimulations (bacille Calmette-Guérin vaccine (BCG), C. albicans (CA), E. coli (EC), H. influenzae (HI), L. monocytogenes (LM), and S. aureus (SA)); SARS-CoV-2 stimulations (irradiated-SARS-CoV-2 (iSARS), SARS-CoV-2 nucleocapsid protein (NCP), SARS-CoV-2 spike Protein S1 (S1) and S2 (S2); and viral/TLR stimulations (hepatitis B antigen (HepB), polycytidylic acid (Poly(I:C)), resiquimod (R848)). Differences were assessed for statistical significance by paired t-tests of the difference in the logarithm of V1 and logarithm of V2 + 28 cytokine concentrations, p-values for each test are represented in respective boxes. Asterisks in the boxes depict significance (*p<0.05, **p<0.01 and ***p<0.001).

Figure 3

Individual cytokine responses to whole‐blood stimulations 28 days after BNT162b2 vaccination. Cytokines are grouped in (A) innate/inflammatory, (B) adaptive/mixed and (C) chemokine categories. The mean ± 95% confidence interval of the log differences (log(V2 + 28) – log(V1)) for each stimulation (bacille Calmette–Guérin vaccine (BCG), C. albicans (CA) E. coli (EC), H. influenzae (HI), L. monocytogenes (LM), and S. aureus (SA), irradiated-SARS-CoV-2 (iSARS), SARS-CoV-2 nucleocapsid protein (NCP), SARS-CoV-2 spike protein S1 (S1) and S2 (S2), hepatitis B antigen (HepB), polycytidylic acid (Poly(I:C)), and R848) are represented in each cytokine plot. Significant results p < 0.05 are depicted in orange.

Figure 4

Cytokine responses to whole‐blood stimulations 182 days after BNT162b2 vaccination. Heatmaps representing (A) the V1 and V2 + 182 cytokine differences and (B) the V2 + 28 and V2 + 182 cytokine differences. The medians of 8 study participants are plotted in the heatmap colour gradient, with red representing increases and blue indicating decreases. Each row represents a stimulation condition, and is separated into three groups: bacterial/fungal stimulations (bacille Calmette-Guérin vaccine (BCG), C. albicans (CA), E. coli (EC), H. influenzae (HI), L. monocytogenes (LM), and S. aureus (SA)); SARS-CoV-2 stimulations (irradiated-SARS-CoV-2 (iSARS), SARS-CoV-2 nucleocapsid protein (NCP), SARS-CoV-2 spike Protein S1 (S1) and S2 (S2); and viral/TLR stimulations (hepatitis B antigen (HepB), polycytidylic acid (Poly(I:C)), resiquimod (R848)). Differences were assessed for statistical significance by the Wilcoxon signed-rank test of the difference in the logarithm of V1 and logarithm of V2 + 182 cytokine concentrations. Asterisks in the boxes depict significance (*p<0.05).

Figure 5

SARS-CoV-2-specific adaptive immunity. (A) Anti-RBD, and (B) anti-spike IgG antibody titres pre- (V1) and post- (V2 + 28, V2 + 182) BNT162b2 vaccination of all participants with matched samples (V1, n=37; V2, n=37; V2 + 182, n=14). These data are separated by previous COVID-19 status by V1, V2 + 28, and V2 + 182 in (C) anti-RBD and (D) anti-spike (No COVID-19: V1, n=35; V2 + 28, n=29, V3 + 182, n=7; COVID-19: V1, n=2; V2 + 28, n=8, V3 + 182, n=7). Differences were assessed for statistical significance using paired t-tests (**p<0.01, ***p<0.001).