Differences in SARS-CoV-2 specific humoral and cellular immune responses after contralateral and ipsilateral COVID-19 vaccination

Abstract

Background: Individual doses of dual-dose vaccine-regimens are sequentially administered into the deltoid muscle, but little attention has so far been paid to the immunological effects of choosing the ipsilateral or the contralateral side for the second dose.

Methods: In an observational study, 303 previously naive individuals were recruited, who received the second dose of the COVID-19 vaccine BNT162b2 on either the ipsilateral (n = 147) or the contralateral side (n = 156). Spike-specific IgG, IgG-avidity, and neutralizing antibodies were quantified using ELISA and a surrogate assay 2 weeks after dose 2. A subgroup of 143 individuals (64 ipsilateral, 79 contralateral) was analysed for spike-specific CD4 and CD8 T-cells using flow-cytometry.

Findings: Median spike-specific IgG-levels did not differ after ipsilateral (4590 (IQR 3438) BAU/ml) or contralateral vaccination (4002 (IQR 3524) BAU/ml, p = 0.106). IgG-avidity was also similar (p = 0.056). However, neutralizing activity was significantly lower after contralateral vaccination (p = 0.024). Likewise, median spike-specific CD8 T-cell levels were significantly lower (p = 0.004). Consequently, the percentage of individuals with detectable CD8 T-cells was significantly lower after contralateral than after ipsilateral vaccination (43.0% versus 67.2%, p = 0.004). Spike specific CD4 T-cell levels were similar in both groups, but showed significantly higher CTLA-4 expression after contralateral vaccination (p = 0.011). These effects were vaccine-specific, as polyclonally stimulated T-cell levels did not differ.

Interpretation: Both ipsilateral and contralateral vaccination induce a strong immune response, but secondary boosting is more pronounced when choosing vaccine administration-routes that allows for drainage by the same lymph nodes used for priming. Higher neutralizing antibody activity and higher levels of spike-specific CD8 T-cells may have implications for protection from infection and severe disease and support general preference for ipsilateral vaccination.

Funding: Financial support was provided in part by the State chancellery of the Saarland to M.S.

Keywords: Antibodies; Avidity; Contralateral; Ipsilateral; Neutralizing activity; T cells; Vaccination.

Fig. 1

Spike-specific IgG, neutralizing antibodies, and CD4 and CD8 T-cells after ipsilateral and contralateral administration of the second dose of the BNT162b2 vaccine. (a) Spike-specific IgG levels, IgG-avidity, and neutralizing activity (dilution 1:16) were determined from all individuals (n = 301) after ipsilateral (n = 145) and contralateral (n = 156) vaccination. (b) Spike-specific CD4 and CD8 T-cells as well as (c) SEB-reactive CD4 and CD8 T-cells were quantified in a subset of individuals (ipsilateral n = 64; contralateral n = 79) after stimulation based on expression of CD69 and IFNγ. Stippled lines denote detection limits as defined by the manufacturer (panel a) or as established in previous studies (panel b).^, Percentages in panel b refer to individuals with specific CD4 and CD8 T-cell levels above detection limit of 0.03%. Statistical analysis was performed using the non-parametric Mann–Whitney test. Bars represent medians with interquartile ranges. (d) Correlation matrix of spike-specific IgG levels, spike-specific neutralizing antibodies, and spike-specific CD4 and CD8 T-cells. Correlation coefficients (including p-values) were calculated according to two-tailed Spearman and displayed using a color code. SEB, Staphylococcus aureus Enterotoxin B. A separate presentation of the data of this figure for female and male study participants is shown in Figure S1.

Fig. 2

Cytokine profile and CTLA-4 expression of spike-specific and SEB-reactive CD4 and CD8 T-cells. (b) Spike-specific and SEB-reactive CD4 and CD8 T-cells were analysed for expression of IFNγ, TNFα and IL-2 alone or in combination after Boolean gating. This allowed distinction of seven subpopulations expressing three, two or a single cytokine. All samples were analysed, but to ensure robust statistics, only individuals with at least 30 cytokine-expressing spike-specific CD4 or CD8 T-cells after normalization to the negative control stimulation were considered (with sample size indicated in the figures). Bars represent means and individual values are displayed by circles. Differences between the groups were analysed using the t-test. (b) Spike-specific and SEB-reactive CD4 and CD8 T-cells were analysed for expression of CTLA-4, which is expressed as median fluorescence intensity (MFI). All samples were analysed, but to ensure robust statistics, this analysis was restricted to samples with at least 20 CD69⁺IFNγ⁺ CD4 or CD8 T-cells (with sample size indicated in the figures). Bars represent medians with interquartile ranges. Differences between the groups were calculated using the Mann Whitney test.

Fig. 3

Adverse events after the first and the second vaccination. (a) Local and systemic adverse events in the first seven days after the first and second vaccination, respectively, were self-reported using a questionnaire. Shown is the percentage of individuals who reported a given adverse event in the ipsilateral or the contralateral group. More detailed statistical analyses are shown in Tables S2–S4. (b) Individual perception of relative severity of the two vaccine doses after ipsilateral or contralateral administration is shown based on whether individuals had felt more affected by the first or by the second vaccination or whether both were scored similar. Analyses was performed using Χ² test.