Immunization with CoronaVac or ChadOx-1 Elicit Distinct Modulation of Monocyte Subtypes and Systemic Inflammatory Status in Older Adults

Background The older adult population was significantly affected by COVID-19 due to immunosenescence, which alters immune elements such as monocytes, impacting immune responses to pathogens and vaccination. Aging-associated systemic inflammation, or inflammaging, can further impair vaccine responses. Although important data exist, the effects of COVID-19 vaccination on monocytes and systemic inflammation in older adults are not fully understood. This study aimed to investigate the impact of COVID-19 vaccination with CoronaVac and ChAdOx-1 on monocyte subtypes and systemic inflammatory status in older adults. Methods Sixty-six older adults (74.74 ± 5.9 years) participated in this study. Blood samples were collected before and 30 days after the second dose of either CoronaVac (n = 48) or ChAdOx-1 (n = 18) to measure IgG levels for SARS-CoV-2, cytokines, and monocyte subtypes (classical, non-classical, and intermediate). Results Both vaccines increased specific IgG levels post-vaccination. The ChAdOx-1 group exhibited higher IgG levels, more classical, non-classical, and intermediate monocytes, and higher IL-6/IL-10 and TNF-α/IL-10 ratios compared to CoronaVac. Conversely, CoronaVac led to higher IFN-γ post-vaccination. Both vaccines promoted distinct modulation of monocyte subtypes and inflammatory status. Conclusion Both vaccines elicited a strong antibody response, but ChAdOx-1 demonstrated better results. Distinct changes in monocyte subtypes and inflammation were observed between the two vaccine groups.