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Background: The adjuvanted recombinant zoster vaccine (RZV), consisting of varicella-zoster virus glycoprotein E (gE) and the AS01B adjuvant system, effectively prevents herpes zoster (HZ). In the absence of a well-defined correlate of protection, it is important to monitor the RZV immune response, as a proxy of clinical effectiveness. Methods: This systematic review examined post-vaccination parameters: humoral and cell-mediated immunity, avidity index, geometric mean concentration of antibody (GMC), and immunity persistence. The meta-analysis used a random-effects model, and subgroup and meta-regression analyses were conducted. Results: Among 37 included articles, after one month from RZV-dose 2, the pooled response rate for anti-gE humoral immunity was 95.2% (95%CI 91.9–97.2), dropping to 77.6% (95%CI 64.7–86.8) during immunosuppression. The anti-gE cell-mediated immunity-specific response reached 84.6% (95%CI 75.2–90.9). Varying factors, such as age, sex, coadministration with other vaccines, prior HZ, or live-attenuated zoster vaccine, did not significantly affect response rates. RZV induced a substantial increase in gE avidity. Immunity persistence was confirmed, with more rapid waning in the very elderly. Conclusions: This systematic review indicates that RZV elicits robust immunogenicity and overcomes immunocompromising conditions. The findings underscore the need for further research, particularly on long-term immunity, and have the potential to support HZ vaccination policies and programs. [ABSTRACT FROM AUTHOR]

The rapid mutation of SARS-CoV-2 has led to multiple rounds of large-scale breakthrough infection and reinfection worldwide. However, the dynamic changes of humoral and cellular immunity responses to several subvariants after infection remain unclear. In our study, a 6-month longitudinal immune response evaluation was conducted on 118 sera and 50 PBMC samples from 49 healthy individuals who experienced BA.5/BF.7/XBB breakthrough infection or BA.5/BF.7-XBB reinfection. By studying antibody response, memory B cell, and IFN-γ secreting CD4+/CD8+ T cell response to several SARS-CoV-2 variants, we observed that each component of immune response exhibited distinct kinetics. Either BA.5/BF.7/XBB breakthrough infection or BA.5/BF.7-XBB reinfection induces relatively high level of binding and neutralizing antibody titers against Omicron subvariants at an early time point, which rapidly decreases over time. Most of the individuals at 6 months post-breakthrough infection completely lost their neutralizing activities against BQ.1.1, CH.1.1, BA.2.86, JN.1 and XBB subvariants. Individuals with BA.5/BF.7-XBB reinfection exhibit immune imprinting shifting and recall pre-existing BA.5/BF.7 neutralization antibodies. In the BA.5 breakthrough infection group, the frequency of BA.5 and XBB.1.16-RBD specific memory B cells, resting memory B cells, and intermediate memory B cells gradually increased over time. On the other hand, the frequency of IFN-γ secreting CD4+/CD8+ T cells induced by WT/BA.5/XBB.1.16 spike trimer remains stable over time. Overall, our research indicates that individuals with breakthrough infection have rapidly declining antibody levels but have a relatively stable cellular immunity that can provide some degree of protection from future exposure to new antigens. [ABSTRACT FROM AUTHOR]

Cellular and humoral immunity exhibit dynamic adaptation to the mutating SARS-CoV-2 virus. It is noteworthy that immune responses differ significantly, influenced by whether a patient has received vaccination or whether there is co-occurrence of naturally acquired and vaccine-induced immunity, known as hybrid immunity. The different immune reactions, conditional on vaccination status and the viral variant involved, bear implications for inflammatory responses, patient outcomes, pathogen transmission rates, and lingering post-COVID conditions. Considering these developments, we have performed a review of recently published literature, aiming to disentangle the intricate relationships among immunological profiles, transmission, the long-term health effects post-COVID infection poses, and the resultant clinical manifestations. This investigation is directed toward understanding the variability in the longevity and potency of cellular and humoral immune responses elicited by immunization and hybrid infection. [ABSTRACT FROM AUTHOR]

The immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) becomes increasingly complex as individuals receive different combinations of vaccine doses and encounter breakthrough infections. Our study focused on the immunogenicity observed over a two-year period in healthy individuals who completed a two-dose series and then experienced booster and/or Omicron infection. In June 2023, we recruited 78 healthcare workers who had previously participated in clinical research initiated in March 2021 at a single medical center in South Korea. At 1, 5, 11, and 25 months after a second dose, we assessed SARS-CoV-2–specific humoral and cellular immune responses. Longitudinal monitoring revealed a significant decline in humoral immunity levels after the second vaccine dose, followed by a substantial increase post-third vaccination or breakthrough infection. In contrast, stable cellular immune responses were consistently observed, with peak humoral and cellular immune measures reached at 25 months after the second dose. Among infection-naïve participants, three-dose vaccinated individuals had decreased neutralizing activity against wild-type (WT) and negative activities against Omicron subvariants BA.2 and BA.4/5, whereas those who received a fourth dose of bivalent BNT had significantly increased neutralizing activity (p < 0.05). All immune metrics tended to increase as the number of vaccine doses increased. Among participants with 4-exposure, homologous vaccination (mRNA × 4) led to higher humoral immunity, whereas heterologous vaccination (ChAd × 2/mRNA × 2) induced stronger cellular responses against multiple SARS-CoV-2 variants by enzyme-linked immunospot assays (p < 0.05). Immune responses from bivalent vaccines or Omicron infection did not show statistically significant differences among exposure number-matched participants (p > 0.05). Omicron exposure significantly increased cross-neutralizing activity, but magnitude of cellular immunity was not significantly altered by Omicron exposure. Our longitudinal study highlights the evolving complexity of SARS-CoV-2 immune responses, showing enhanced immunity with multiple vaccine doses and robust cellular responses from heterologous vaccination. These findings emphasize the need for ongoing surveillance to optimize vaccination strategies against emerging variants. [ABSTRACT FROM AUTHOR]