Comparison of SARS-CoV-2 Immune Responses Following Vaccination with Comirnaty (Pfizer) and Vaxzevria (AstraZeneca) in Healthy Individuals with or without Prior SARS-CoV-2 Infection

Zdzisława Kondera- Anasz¹Emilia Justyna Morawiec^2,3*Roksana Duszkiewicz¹Filip Hajdrowski¹Andrzej Wiczkowski²

• ¹Department of Immunology, Faculty of Medicine in Zabrze, Academy of Silesia, Katowice, Poland
• ²Department of Microbiology, Faculty of Medicine in Zabrze, Academy of Silesia, Katowice, Poland
• ³Gyncentrum, Laboratory of Molecular Biology and Virology, Katowice, Poland

This study compares the immune responses of healthy individuals—with or without prior SARS-CoV-2 infection—after Comirnaty (Pfizer) and Vaxzevria (AstraZeneca) vaccinations. For this study, a total cohort of 134 volunteers was analyzed. Among the 71 Comirnaty recipients, 36 had prior COVID-19, while 33 of the 63 Vaxzevria recipients had a history of infection. Individuals’ immune responses were assessed after second and third doses by measuring the levels of anti-SARS-CoV-2 Immunoglobulin G (IgG) and specific interferon-gamma (IFN-γ) release assay (IGRA). Statistically significant differences were observed in IgG and IFN-γ concentrations between groups receiving different vaccines. Higher IgG levels were noted in individuals vaccinated with Comirnaty than in those vaccinated with Vaxzevria, especially after the third dose. Similarly, IFN-γ production was significantly higher in individuals who received Comirnaty vaccination, suggesting a stronger T-cell-mediated immune response. Prior infection influenced the magnitude of individuals’ immune responses, in that previously infected individuals displayed higher IgG and IFN-γ levels. Further hematologic analysis revealed notable differences in the two immune activation patterns between the vaccines’ immune activation patterns in terms of white blood cell counts, neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR). The findings highlighted varying vaccine-induced immune responses, depending on the vaccine type, prior infection status, and the number of administered doses. These results contribute to a better understanding of the differential immune memory induced by mRNA-based and adenoviral vector–based vaccines and emphasize the importance of booster doses in maintaining robust immunity against SARS-CoV-2.