Long-lasting humoral and cellular memory immunity to vaccinia virus Tiantan provides pre-existing immunity against mpox virus in Chinese population.

Investigating immune memory to vaccinia virus and pre-existing immunity to mpox virus (MPXV) among the population is crucial for the global response to this ongoing mpox epidemic. Blood was sampled from vaccinees inoculated with vaccinia virus Tiantan (VTT) strain born before 1981 and unvaccinated control subjects born since 1982. After at least 40 years of the inoculation, 60% or 5% VTT vaccinees possess neutralizing antibodies (NAbs) to VTT or MPXV, with at least 50% having T cell memory to VTT protein antigens. Notably, 46.7% vaccinees show pre-existing T cell responses to MPXV. Broad pre-existing CD8+ T cell reactivities to MPXV are detected not only against conserved epitopes but also against variant epitopes between VTT and MPXV. Persistent NAbs and T cell memory to VTT among vaccinees, along with pre-existing T cells to MPXV among both vaccinees and the unvaccinated population, indicate a particular immune barrier to mpox.

Inactivated vaccine fueled adaptive immune responses to Omicron in 2-year COVID-19 convalescents.

Over 3 years, humans have experienced multiple rounds of global transmission of SARS-CoV-2 and its variants. In addition, the widely used vaccines against SARS-CoV-2 involve multiple strategies of development and inoculation. Thus, the acquired immunity established among humans is complicated, and there is a lack of understanding within a panoramic vision. Here, we provided the special characteristics of the cellular and humoral responses in 2-year convalescents after inactivated vaccines, in parallel to vaccinated COVID-19 naïve persons and unvaccinated controls. The decreasing trends of the IgG, IgA, and NAb, but not IgM of the convalescents were reversed by the vaccination. Both cellular and humoral immunity in convalescents after vaccination were higher than the vaccinated COVID-19 naïve persons. Notably, inoculation with inactivated vaccine fueled the NAb to BA.1, BA.2, BA.4, and BA.5 in 2-year convalescents, much higher than the NAb during 6 months and 1 year after symptoms onset. And no obvious T cell escaping to the S protein was observed in 2-year convalescents after inoculation. The study provides insight into the complicated features of human acquired immunity to SARS-CoV-2 and variants in the real world, indicating that promoting vaccine inoculation is essential for achieving herd immunity against emerging variants, especially in convalescents.