Impact of Immune Abnormalities on COVID-19 Vaccine Effectiveness in Infected Patients

Objective To assess the protective effect of COVID-19 vaccines in patients with varying immune states by analyzing lactate dehydrogenase (LDH), C-reactive protein (CRP), and D-dimer (D-Di) levels in COVID-19-infected individuals under different vaccination scenarios and immune statuses. Methods This is a single-center retrospective study involving 338 SARS-CoV-2-infected patients treated at a tertiary medical center in Foshan, China, between November 2022 and January 2023. The primary outcome was the vaccine's protective effect on LDH, CRP, and D-Di levels. Results Vaccinated patients had shorter hospital stays and less severe lung involvement (P < 0.05), particularly in immunocompromised individuals. In immunocompromised patients, LDH and CRP levels were elevated, but in the vaccine group, fewer patients developed abnormally high CRP, D-Di, and coagulation-related complications. Vaccination reduced LDH and CRP levels in immunocompetent patients and lowered CRP levels regardless of immune status. In addition, people who are both immunocompromised and vaccinated have a higher risk of developing microthrombosis. Conclusions COVID-19 vaccination generally improves LDH, CRP, and D-Di levels, particularly in immunocompromised patients, supporting vaccination efforts. However, a subset of immunocompromised and vaccinated patients exhibited higher D-Di levels upon hospital admission, suggesting a complex interplay between vaccination, immune status, and the risk of microthrombosis. This finding emphasizes the need for further investigation into the role of immune function in disease severity and vaccine response.