Pre-existing T cell immunity determines the frequency and magnitude of cellular immune response to two doses of mRNA vaccine against SARS-CoV-2

• Published in: Vaccine: X Vol. 11; p. 100165
• Main Authors: Casado, José L., Vizcarra, Pilar, Haemmerle, Johannes, Velasco, Héctor, Martín-Hondarza, Adrián, Rodríguez-Domínguez, Mario J., Velasco, Tamara, Martín, Sara, Romero-Hernández, Beatriz, Fernández-Escribano, Marina, Vallejo, Alejandro
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-08-2022; Elsevier
• Subjects: Cellular response; mRNA vaccine; Pre-existing immunity; SARS-CoV-2 humoral response; Short communication; SARS-CoV-2 humoral response; COVID-19; SARS-CoV-2; AU; Pre-existing immunity; RT-PCR; IgG; S protein; CLIA; Cellular response; mRNA vaccine; IgG, immunoglobulin G; SARS-CoV-2, Severe acute respiratory syndrome coronavirus 2; S protein, Spike protein; RT-PCR, retrotranscriptasepolymerase chain reaction; CLIA, chemoluminiscent immunoassay; AU, arbitrary units; COVID-19, Coronavirus disease 2019
• ISSN: 2590-1362; 2590-1362
• DOI: 10.1016/j.jvacx.2022.100165

•Lack of CD4 T-cell response to first/second dose of mRNA vaccine was observed in 21% and 12% of health care workers (HCWs).•T-cell response was greater in frequency/magnitude in HCWs with pre-existing immunity, due due to infection or cross-reactivity.•Pre-existing immunity correlated with the magnitude of specific antibodies production after vaccination.
Little is known about the factors associated with lack of T-cell response to mRNA vaccines against SARS-CoV-2. In a prospective cohort of 61 health care workers (HCWs), 21% and 16% after the first dose of mRNA BNT162b vaccine, and 12% and 7% after the second dose, showed lack of CD4+ and CD8+ T-cell response, respectively. Pre-existing T-cell immunity, due to past infection (46%) or cross-reactive cellular response (26%), was significantly associated with T-cell response in frequency (CD4+ T-cell, 100% vs 82% after two doses; p = 0.049) and in the magnitude of T-cell response during follow up. Furthermore, baseline CD4+ T-cell correlated positively with the titer of specific IgG-antibodies after first and second vaccine dose. Our data demonstrate that cross-reactive T-cells correlate with a better cellular response as well as an enhanced humoral response, and we confirm the close correlation of humoral and cellular response after mRNA vaccination.