B- and T-cell immune responses elicited by the Comirnaty® COVID-19 vaccine in nursing-home residents

Abstract

Objectives: The immunogenicity of the Comirnaty® vaccine against coronavirus disease 2019 (COVID-19) has not been adequately studied in elderly people with comorbidities. We assessed antibody and T-cell responses targeted to the S protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) following full vaccination in nursing-home residents.

Methods: Sixty nursing-home residents (44 female, age 53-100 years), of whom ten had previously been diagnosed with COVID-19, and 18 healthy controls (15 female, age 27-54 years) were recruited. Pre- and post-vaccination blood specimens were available for quantification of total antibodies binding the SARS-CoV-2 S protein and for enumeration of SARS-CoV-2 S-reactive IFN-γ CD4⁺ and CD8⁺ T cells by flow cytometry.

Results: The seroconversion rate in (presumably) SARS-CoV-2-naïve nursing-home residents (41/43, 95.3%) was similar to that in controls (17/18, 94.4%). A booster effect was documented in post-vaccination samples of nursing-home residents with prior COVID-19. Plasma antibody levels were higher (p < 0.01) in recovered nursing-home residents (all 2500 IU/mL) than in individuals across the other two groups (median 1120 IU/mL in naïve nursing-home residents and 2211 IU/ml in controls). A large percentage of nursing-home residents had SARS-CoV-2 S-reactive IFN-γ CD8⁺ (naïve 31/49, 63.2%; recovered 8/10, 80%) or CD4⁺ T cells (naïve 35/49, 71.4%; recovered 7/10, 70%) at baseline, in contrast to healthy controls (3/17, 17.6% and 5/17, 29%, respectively). SARS-CoV-2 IFN-γ CD8⁺ and CD4⁺ T-cell responses were documented in 88% (15/17) and all control subjects after vaccination, respectively, but only in 65.5% (38/58) and 22.4% (13/58) of nursing-home residents. Overall, the median frequency of SARS-CoV-2 IFN-γ CD8⁺ and CD4⁺ T cells in nursing-home residents decreased in post-vaccination specimens, whereas it increased in controls.

Conclusion: The Comirnaty COVID-19 vaccine elicits robust SARS-CoV-2 S antibody responses in nursing-home residents. Nevertheless, the rate and frequency of detectable SARS-CoV-2 IFN-γ T-cell responses after vaccination was lower in nursing-home residents than in controls.

Keywords: Comirnaty®COVID-19 vaccine; Nursing-home residents; SARS-CoV-2; SARS-CoV-2 S T cells; SARS-CoV-2 S antibodies.

Fig. 1

Severe acute respiratory syndrome coronavirus 2 S protein (SARS-CoV-2 S) plasma antibody levels as measured by Roche Elecsys® Anti-SARS-CoV-2 S immunoassay in nursing-home residents (NHRs) with or without documented prior SARS-CoV-2 infection and in healthy controls following complete vaccination. The limit of detection of the assay is 0.4 IU/mL and its quantification range is between 0.8 and 250 IU/mL. Plasma specimens were further diluted (1/10) for antibody quantification when appropriate. Bars represent median levels and the asterisks indicate a significant difference in antibody levels across groups (p < 0.01).

Fig. 2

Individual kinetics of severe acute respiratory syndrome coronavirus 2 S protein- (SARS-CoV-2 S-)reactive IFN-γ-producing CD8⁺ or CD4⁺ T-cell levels in presumably SARS-CoV-2-naïve (A) and recovered (B) nursing-home residents (NHRs).

Fig. 3

Box plots depicting pre- and post-vaccination severe acute respiratory syndrome coronavirus 2 S protein- (SARS-CoV-2 S-)reactive IFN-γ-producing CD8⁺ or CD4⁺ T-cell levels in presumably SARS-CoV-2-naïve (A) or recovered (B) nursing-home residents (NHRs) and controls (C). The p values for comparisons are shown.

figs1

figs2