Hybrid immunity by two COVID-19 mRNA vaccinations and one breakthrough infection provides a robust and balanced cellular immune response as basic immunity against severe acute respiratory syndrome coronavirus 2.

This longitudinal prospective controlled multicenter study aimed to monitor immunity generated by three exposures caused by breakthrough infections (BTI) after COVID-19-vaccination considering pre-existing cell-mediated immunity to common-corona-viruses (CoV) which may impact cellular reactivity against SARS-CoV-2. Anti-SARS-CoV-2-spike-IgG antibodies (anti-S-IgG) and cellular reactivity against Spike-(S)- and nucleocapsid-(N)-proteins were determined in fully-vaccinated (F) individuals who either experienced BTI (F+BTI) or had booster vaccination (F+Booster) compared to partially vaccinated (P+BTI) and unvaccinated (U) from 1 to 24 weeks post PCR-confirmed infection. High avidity anti-S-IgG were found in F+BTI compared to U, the latter exhibiting increased long-lasting pro-inflammatory cytokines to S-stimulation. CoV was associated with higher cellular reactivity in U, whereas no association was seen in F. The study illustrates the induction of significant S-specific cellular responses in F+BTI building-up basic immunity by three exposures. Only U seem to benefit from pre-existing CoV immunity but demonstrated inflammatory immune responses compared to F+BTI who immunologically benefit from enhanced humoral and cellular immunity after BTI. This study demonstrates that individuals with hybrid immunity from COVID-19-vaccination and BTI acquire a stable humoral and cellular immune response that is maintained for at least 6 months. Our findings corroborate recommendations by health authorities to build on basic immunity by three S-protein exposures.

Almanzar G ，Koosha K ，Vogt T ，Stein A ，Ziegler L ，Asam C ，Weps M ，Schwägerl V ，Richter L ，Hepp N ，Fuchs A ，Wagenhäuser I ，Reusch J ，Krone M ，Geldmacher C ，Protzer U ，Steininger P ，Überla K ，Wagner R ，Liese J ，Prelog M ... -  《-》

Heterologous and homologous COVID-19 mRNA vaccination schemes for induction of basic immunity show similar immunogenicity regarding long-term spike-specific cellular immunity in healthcare workers.

Healthcare workers (HCWs) are recommended to receive at least three spike-antigen exposures to generate basic immunity and to mediate herd protection of vulnerable patients. So far, less attention has been put on the cellular immune response induced by homologous (three BTN162b2mRNA doses) or heterologous (mRNA-1273 as third dose building on two BTN162bmRNA doses) and the immunological impact of breakthrough infections (BTIs). Therefore, in 356 vaccinated HCWs with or without BTIs the Anti-SARS-CoV-2-Spike-IgG concentrations and avidities and B- and T-cell-reactivity against SARS-CoV-2-Spike-S1- and Nucleocapsid-antigens were assessed with Interferon-gamma-ELISpot and by flow-cytometry. HCWs who had hybrid immunity due to BTIs exhibited strong T-cell-reactivity against the Spike-S1-antigen. A lasso regression model revealed a significant reduction in T-cell immune responses among smokers (p < 0.0001), with less significant impact observed for age, sex, heterologous vaccination, body-mass-index, Anti-Nucleocapsid T-cell reactivity, days since last COVID-19-immunization, and Anti-SARS-CoV-2-Spike-IgG. Although subgroup analysis revealed higher Anti-SARS-CoV-2-Spike-IgG after heterologous vaccination, similar cellular reactivity and percentages of Spike-reactive T- and B-cells were found between homologous and heterologous vaccination. Anti-SARS-CoV-2-Spike-IgG concentrations and avidity significantly correlated with activated T-cells. CD4 + and CD8 + responses correlated with each other. A strong long-term cellular immune response should be considered as baseline for recommendations of booster doses in HCWs with prioritization of smokers. HCWs presented significant T-cellular reactivity towards Spike-S1-antigen with particularly strong responses in hybrid immunized HCWs who had BTIs. HCWs without BTI presented similar percentages of Spike-specific B- and T-cells between homologous or heterologous vaccination indicating similar immunogenicity for both mRNA vaccines, BNT162b2mRNA and mRNA-1273.

Wagenhäuser I ，Almanzar G ，Förg FB ，Stein A ，Eiter I ，Reusch J ，Mees J ，Herzog A ，Vogel U ，Frey A ，Lâm TT ，Schubert-Unkmeir A ，Dölken L ，Kurzai O ，Frantz S ，Gabel A ，Petri N ，Prelog M ，Krone M ... -  《-》

First SARS-CoV-2 Omicron infection as an effective immune booster among mRNA vaccinated individuals: final results from the first phase of the PRIBIVAC randomised clinical trial.

Understanding how SARS-CoV-2 breakthrough infections impacts the breadth of immune responses against existing and pre-emergent SARS-CoV-2 strains is needed to develop an evidence-based long-term immunisation strategy. We performed a randomised, controlled trial to assess the immunogenicity of homologous (BNT162b2) versus heterologous (mRNA-1273) booster vaccination in 100 BNT162b2-vaccinated infection-naïve individuals enrolled from October 2021. Post hoc analysis was performed to assess the impact of SARS-CoV-2 infection on humoral and cellular immune responses against wild-type SARS-CoV-2 and/or Omicron subvariants. 93 participants completed the study at day 360. 71% (66/93) of participants reported first SARS-CoV-2 Omicron infection by the end of the study with similar proportions of infections between homologous and heterologous booster groups (72.3% [34/47] vs 69.6% [32/46]; p = 0.82). Mean wildtype SARS-CoV-2 anti-S-RBD antibody level was significantly higher in heterologous booster group compared with homologous group at day 180 (14,588 IU/mL; 95% CI, 10,186-20,893 vs 7447 IU/mL; 4646-11,912; p = 0.025). Participants who experienced breakthrough infections during the Omicron BA.1/2 wave had significantly higher anti-S-RBD antibody levels against wildtype SARS-CoV-2 and antibody neutralisation against BA.1 and pre-emergent BA.5 compared with infection-naïve participants. Regardless of hybrid immunity status, wildtype SARS-CoV-2 anti-S-RBD antibody level declined significantly after six months post-booster or post-SARS-CoV-2 infection. Booster vaccination with mRNA-1273 was associated with significantly higher antibody levels compared with BNT162b2. Antibody responses are narrower and decline faster among uninfected, vaccinated individuals. Boosters may be more effective if administered shortly before infection outbreaks and at least six months after last infection or booster. Singapore NMRC, USFDA, MRC.

Poh XY ，Lee IR ，Tan CW ，Chavatte JM ，Fong SW ，Goh YS ，Rouers A ，Wong N ，Torres-Ruesta A ，Mah SYY ，Yeoh AYY ，Gandhi M ，Rahman N ，Chin YQ ，Lim JJ ，Yoong TJK ，Rao S ，Chia PY ，Ong SWX ，Lee TH ，Sadarangani SP ，Lin RJH ，Lim DRX ，Chia W ，Renia L ，Ren EC ，Lin RTP ，Lye DC ，Wang LF ，Ng LFP ，Young BE ... -  《EBioMedicine》

Effects of the induction of humoral and cellular immunity by third vaccination for SARS-CoV-2.

To control the spread of severe disease caused by mutant strains of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), it is necessary to determine whether continued vaccination enhances humoral and cellular immunity. In this study, we examined the changes in humoral and cellular immunity to SARS-CoV-2 after administration of the third vaccination in Japanese adults who had received the second dose of messenger ribonucleic acid (mRNA)-1273 vaccine and the third vaccination (BNT162b2 or mRNA-1273). We measured anti-spike antibodies in immunoglobulin G (IgG) and anti-nucleocapsid IgG titers in the serum of the vaccinated subjects. To evaluate cellular immunity, the peripheral blood mononuclear cells of inoculated individuals were cultured with spiked proteins, including those of the SARS-CoV-2 conventional strain and Omicron strain, and then subjected to enzyme-linked immunospot (ELISPOT). The results revealed that the anti-SARS-CoV-2 spike protein antibody titer increased after the third vaccination and was maintained; however, a decrease was observed at 6 months after vaccination. SARS-CoV-2 antigen-specific T helper (Th)1 and Th2 cell responses were also induced after the third vaccination and were maintained for 6 months after vaccination. Furthermore, induction of cellular immunity against Omicron strains by the omicron non-compliant vaccines, BNT162b2 or mRNA-1273, was observed. These findings demonstrate the effectiveness of vaccination against unknown mutant strains that may occur in the future and provide important insights into vaccination strategies.

Murayama G ，Kusaoi M ，Horiuchi Y ，Tabe Y ，Naito T ，Ito S ，Yamaji K ，Tamura N ... -  《-》

Characterization of SARS-CoV-2-Specific Humoral and Cellular Immune Responses Induced by Inactivated COVID-19 Vaccines in a Real-World Setting.

While the immunogenicity of inactivated vaccines against coronavirus disease 2019 (COVID-19) has been characterized in several well-conducted clinical trials, real-world evidence concerning immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) raised by such vaccines is currently missing. Here, we comprehensively characterized various parameters of SARS-CoV-2-specific cellular and humoral immune responses induced by inactivated COVID-19 vaccines in 126 individuals under real-world conditions. After two doses of vaccination, S-receptor binding domain IgG (S-RBD IgG) and neutralizing antibody (NAb) were detected in 87.06% (74/85) and 78.82% (67/85) of individuals, respectively. Female participants developed higher concentrations of S-RBD IgG and NAb compared to male vaccinees. Interestingly, a longer dosing interval between the first and second vaccination resulted in a better long-term SARS-CoV-2 S-RBD IgG response. The frequencies of CD4+ T cells that produce effector cytokines (IFN-γ, IL-2, and TNF-α) in response to stimulation with peptide pools corresponding to the SARS-CoV-2 spike (S), nucleocapsid (N) or membrane (M) protein were significantly higher in individuals received two doses of vaccine than those received one dose of vaccine and unvaccinated individuals. S, N, or M-specific CD4+ and CD8+ T cell responses were detectable in 95.83% (69/72) and 54.16% (39/72) of double-vaccinated individuals, respectively. The longitudinal analysis demonstrated that CD4+ T cell responses recognizing S, N, and M waned quickly after a single vaccine dose, but were boosted and became more sustained following a second dose. Overall, we provide a comprehensive characterization of immune responses induced by inactivated COVID-19 vaccines in real-world settings, suggesting that both humoral and cellular SARS-CoV-2-specific immunity are elicited in the majority of individuals after two doses of inactivated COVID-19 vaccines.

Li Z ，Xiang T ，Liang B ，Deng H ，Wang H ，Feng X ，Quan X ，Wang X ，Li S ，Lu S ，Yang X ，Wang B ，Zelinskyy G ，Trilling M ，Sutter K ，Lu M ，Dittmer U ，Yang D ，Zheng X ，Liu J ... -  《Frontiers in Immunology》