Individuals with a recent common cold coronavirus infection, which leads to preexisting immunity against SARS-CoV-2, displayed a less severe course of COVID-19.However, the relationship between pre-existing immunity against SARS-CoV-2 and the inactivated-vaccine-induced immune response is still unknown. Here, 31 healthcare workers who received standard two doses of inactivated COVID-19 vaccines (Weeks 0 and 4, respectively) were enrolled, vaccine-induced neutralization and T cell responses were detected, and the correlation between the pre-existing SARS-CoV-2-specific immunity was analyzed. We found the SARS-CoV-2-specific antibodies, pseudovirus neutralization test (pVNT) titers, and spike-specific interferon gamma (IFN-γ) production in CD4 + and CD8 + T cells were significantly elevated after two doses of inactivated vaccines. Interestingly, the pVNT titers after the second dose of vaccination displayed no significant correlation with the preexisting SARS-CoV-2-specific antibodies or B cells, nor the pre-existing spikespecific CD4 + T cells. Notably, the spike-specific T cell response after the second dose of vaccination was positively correlated with the pre-existing receptor binding domain (RBD)-specific B cells and CD4 + T cells, which were documented by the frequencies of RBD-binding B cells, the breadth of RBD-specific B cell epitopes, and the frequency of IFN-γ-expressing RBD-specific CD4 + T cells. Overall, the inactivated-vaccine-induced T cell responses, not the inactivated-vaccine-induced neutralization, closely correlated with pre-existing immunity to SARS-CoV-2. Our results provide a better understanding of inactivated-vaccine-induced immunity and help predict the immunogenicity induced by inactivated vaccines in individuals.

Problem Hepatitis B virus (HBV) infection is more likely to develop a state of chronicity in early life, particularly mother‐to‐child transmission (MTCT) of HBV in the fetus during pregnancy. Till now, little is known about the impact of chronic HBV infection on the immune status of the maternal‐fetus interface, and the immune profile of placental lymphocytes in MTCT of HBV is poorly understood. Method of Study Thirteen term pregnant women with chronic HBV infection (HBV‐PW) and thirteen normal pregnant women as healthy control (HC‐PW) were enrolled. The profile of placental immune cells and paired peripheral blood were analyzed by flow cytometry and immunohistochemistry. Results Compared with HC‐PW, the frequency of CD8+ T cells from the term placenta of HBV‐PW was significantly reduced. These cells showed decreased expression of activation molecules CD69 and HLA‐DR; thus, decidual CD8+ T cells from HBV‐PW demonstrated hypofunctional signature as evidenced by significantly reduced production of IFN‐γ, as well as compromised ability of degranulation and proliferation. Conclusions These findings supported that hypoactivated decidual CD8+ T cells might possess compromised ability in chronically HBV‐infected term pregnant women. Our study provides robust evidence for the necessity and importance of antiviral intervention in HBV‐PW to prevent MTCT of HBV.