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. 2023 Sep 6;24(18):13728.
doi: 10.3390/ijms241813728.

Humoral and Cellular Immune Response Elicited by the BNT162b2 COVID-19 Vaccine Booster in Elderly

Daniela Dalla Gasperina  1 , Giovanni Veronesi  2 , Carlo M Castelletti  3 , Stefania Varchetta  4 , Sabrina Ottolini  5 , Dalila Mele  6 , Giuseppe Ferrari  3 , Amruth K B Shaik  7 , Fabrizio Celesti  8 , Francesco Dentali  9 , Roberto S Accolla  7 , Greta Forlani  7
Affiliations

Humoral and Cellular Immune Response Elicited by the BNT162b2 COVID-19 Vaccine Booster in Elderly

Daniela Dalla Gasperina et al. Int J Mol Sci. .

Abstract

Although the safety and efficacy of COVID-19 vaccines in older people are critical to their success, little is known about their immunogenicity among elderly residents of long-term care facilities (LTCFs). A single-center prospective cohort study was conducted: a total IgG antibody titer, neutralizing antibodies against Wild-type, Delta Plus, and Omicron BA.2 variants and T cell response, were measured eight months after the second dose of BNT162b2 vaccine (T0) and at least 15 days after the booster (T1). Forty-nine LTCF residents, with a median age of 84.8 ± 10.6 years, were enrolled. Previous COVID-19 infection was documented in 42.9% of the subjects one year before T0. At T1, the IgG titers increased up to 10-fold. This ratio was lower in the subjects with previous COVID-19 infection. At T1, IgG levels were similar in both groups. The neutralizing activity against Omicron BA.2 was significantly lower (65%) than that measured against Wild-type and Delta Plus (90%). A significant increase of T cell-specific immune response was observed after the booster. Frailty, older age, sex, cognitive impairment, and comorbidities did not affect antibody titers or T cell response. In the elderly sample analyzed, the BNT162b2 mRNA COVID-19 vaccine produced immunogenicity regardless of frailty.

Keywords: BNT162b2 mRNA COVID-19 vaccine; Omicron BA.2; cellular immunity; long-term care facilities elderly residents; neutralizing antibodies.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the study’s design; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Humoral response to BNT162b2 vaccination in elderly. Distribution of serum IgG at T0 and T1 in all the recruited individuals and according to their exposure to SARS-CoV-2 infection after primary vaccination cycle. In each group, the horizontal line represents the sample median, while the vertical line represents the interquartile range. T0 = pre-booster; T1 = post-booster. Statistical analyses were reported in Table 2.
Figure 2
Figure 2
BNT162b2 booster in elderly elicits strong neutralizing antibodies activity against Wild-type and Delta Plus variants but weaker against Omicron BA.2. Nab percentage distribution of SARS-CoV-2 variants at T0 (orange) and T1 (light blue) according to SARS-CoV-2 variants.
Figure 3
Figure 3
Neutralizing activity against Omicron BA.2 variant positivity correlates with IgG titer before and after the booster dose of BNT162b2. Scatter plot for Nab percentage and serum IgG at T0 (A) and at T1 (B) in all the recruited individuals and according to their exposure to SARS-CoV-2 infection after primary vaccination cycle. Dashed lines represent the reference standards values.
Figure 4
Figure 4
Cellular response to BNT162b2 vaccination in elderly. PBMCs collected at T0 and at T1 were stimulated for 24h with RBD-15 mer overlapping peptides. Each data point represents the normalized mean spot count from duplicate wells for one study participant, after subtraction of the non-stimulated control in the overall sample (A) and according to previous SARS-CoV-2 infection (B) Results were given as IFN-γ spot-forming units (SFU)/106 PBMC. The positive cut-off was set at 10 IFN-γ SFU/106 PBMC. Correlations between IgG levels and the cumulative SFU responses at T0 and T1 in overall population ((C,F), respectively), and according to prior SARS-CoV-2 infection ((D,E,G,H), respectively) as assessed by Pearson correlation. r, correlation coefficient. **** p < 0.00001.
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