Journal Article

A 12-month follow-up of the immune response to SARS-CoV-2 primary vaccination: evidence from a real-world study

Palamara, Anna Teresa, Clerici, Pierangelo, Fallucca, Alessandra, Abrignani, Sergio, Giberti, Irene, Domnich, Alexander, De Paschale, Massimo, Olivetta, Eleonora, Diaco, Fabiana, Schiavoni, Ilaria, Fortunato, Francesca, Brusaferro, Silvio, Trentini, Filippo, Baldo, Vincenzo, Baldovin, Tatjana, Lodi, Vittorio, Leone, Pasqualina, Fedele, Giorgio, Grifantini, Renata, Stefanelli, Paola, Bandera, Alessandra, Mastroianni, Claudio Maria, Prato, Rosa, Restivo, Vincenzo, Vitale, Francesco, Fiore, Stefano, Merler, Stefano, Di Martino, Angela, Gori, Andrea, Lazzarotto, Tiziana

2023

Overview

A real-world population-based longitudinal study, aimed at determining the magnitude and duration of immunity induced by different types of vaccines against COVID-19, started in 2021 by enrolling a cohort of 2,497 individuals at time of their first vaccination. The study cohort included both healthy adults aged ≤65 years and elderly subjects aged >65 years with two or more co-morbidities. Here, patterns of anti-SARS-CoV-2 humoral and cell-mediated specific immune response, assessed on 1,182 remaining subjects, at 6 (T6) and 12 months (T12) after the first vaccine dose, are described. At T12 median anti-Spike IgG antibody levels were increased compared to T6. The determinants of increased anti-Spike IgG were the receipt of a third vaccine dose between T6 and T12 and being positive for anti-Nucleocapside IgG at T12, a marker of recent infection, while age had no significant effect. The capacity of T12 sera to neutralize in vitro the ancestral B strain and the Omicron BA.5 variant was assessed in a subgroup of vaccinated subjects. A correlation between anti-S IgG levels and sera neutralizing capacity was identified and higher neutralizing capacity was evident in healthy adults compared to frail elderly subjects and in those who were positive for anti-Nucleocapside IgG at T12. Remarkably, one third of T12 sera from anti-Nucleocapside IgG negative older individuals were unable to neutralize the BA.5 variant strain. Finally, the evaluation of T-cell mediated immunity showed that most analysed subjects, independently from age and comorbidity, displayed Spike-specific responses with a high degree of polyfunctionality, especially in the CD8 compartment. In conclusion, vaccinated subjects had high levels of circulating antibodies against SARS-CoV-2 Spike protein 12 months after the primary vaccination, which increased as compared to T6. The enhancing effect could be attributable to the administration of a third vaccine dose but also to the occurrence of breakthrough infection. Older individuals, especially those who were anti-Nucleocapside IgG negative, displayed an impaired capacity to neutralize the BA.5 variant strain. Spike specific T-cell responses, able to sustain immunity and maintain the ability to fight the infection, were present in most of older and younger subjects assayed at T12.

• Publisher: Frontiers Media SA,Frontiers Media S.A
• Subject: Adult / Aged / Antibodies / CD8 antigen / Cell-mediated immunity / Comorbidity / COVID-19 / COVID-19 - prevention & control / COVID-19 Vaccines / Cytokines / Disease transmission / Follow-Up Studies / Humans / Immune response / Immune response (cell-mediated) / Immune response (humoral) / Immunity (Disease) / Immunity, Cellular / Immunoassay / Immunoglobulin G / Infections / Investigations / Longitudinal Studies / Lymphocytes T / mRNA vaccines / Pandemics / Peptides / Population studies / Proteins / SARS-CoV-2 / serology / Severe acute respiratory syndrome coronavirus 2 / Spike protein / T-cell / Vaccination / Vaccines