Association of systemic adverse reaction patterns with long-term dynamics of humoral and cellular immunity after coronavirus disease 2019 third vaccination.

The objective of this study was to clarify the impact of adverse reactions on immune dynamics. We investigated the pattern of systemic adverse reactions after the second and third coronavirus disease 2019 (COVID-19) vaccinations and their relationship with immunoglobulin G against severe acute respiratory syndrome coronavirus 2 spike 1 protein titers, neutralizing antibody levels, peak cellular responses, and the rate of decrease after the third vaccination in a large-scale community-based cohort in Japan. Participants who received a third vaccination with BNT162b2 (Pfizer/BioNTech) or mRNA-1273 (Moderna), had two blood samples, had not had COVID-19, and had information on adverse reactions after the second and third vaccinations (n = 2198) were enrolled. We collected data on sex, age, adverse reactions, comorbidities, and daily medicine using a questionnaire survey. Participants with many systemic adverse reactions after the second and third vaccinations had significantly higher humoral and cellular immunity in the peak phase. Participants with multiple systemic adverse reactions after the third vaccination had small changes in the geometric values of humoral immunity and had the largest geometric mean of cellar immunity in the decay phase. Systemic adverse reactions after the third vaccination helped achieve high peak values and maintain humoral and cellular immunity. This information may help promote uptake of a third vaccination, even among those who hesitate due to adverse reactions.

Vaccine-induced protection against SARS-CoV-2 requires IFN-γ-driven cellular immune response.

The overall success of worldwide mass vaccination in limiting the negative effect of the COVID-19 pandemics is inevitable, however, recent SARS-CoV-2 variants of concern, especially Omicron and its sub-lineages, efficiently evade humoral immunity mounted upon vaccination or previous infection. Thus, it is an important question whether these variants, or vaccines against them, induce anti-viral cellular immunity. Here we show that the mRNA vaccine BNT162b2 induces robust protective immunity in K18-hACE2 transgenic B-cell deficient (µMT) mice. We further demonstrate that the protection is attributed to cellular immunity depending on robust IFN-γ production. Viral challenge with SARS-CoV-2 Omicron BA.1 and BA.5.2 sub-variants induce boosted cellular responses in vaccinated µMT mice, which highlights the significance of cellular immunity against the ever-emerging SARS-CoV-2 variants evading antibody-mediated immunity. Our work, by providing evidence that BNT162b2 can induce significant protective immunity in mice that are unable to produce antibodies, thus highlights the importance of cellular immunity in the protection against SARS-CoV-2.

Short- and Long-Interval Prime-Boost Vaccination with the Candidate Vaccines MVA-SARS-2-ST and MVA-SARS-2-S Induces Comparable Humoral and Cell-Mediated Immunity in Mice.

The COVID-19 pandemic caused significant human health and economic consequences. Due to the ability of SARS-CoV-2 to spread rapidly and to cause severe disease and mortality in certain population groups, vaccines are essential for controlling the pandemic in the future. Several licensed vaccines have shown improved protection against SARS-CoV-2 after extended-interval prime-boost immunizations in humans. Therefore, in this study, we aimed to compare the immunogenicity of our two Modified Vaccinia virus Ankara (MVA) based COVID-19 candidate vaccines MVA-SARS-2-S and MVA-SARS-2-ST after short- and long-interval prime-boost immunization schedules in mice. We immunized BALB/c mice using 21-day (short-interval) or 56-day (long-interval) prime-boost vaccination protocols and analyzed spike (S)-specific CD8 T cell immunity and humoral immunity. The two schedules induced robust CD8 T cell responses with no significant differences in their magnitude. Furthermore, both candidate vaccines induced comparable levels of total S, and S2-specific IgG binding antibodies. However, MVA-SARS-2-ST consistently elicited higher amounts of S1-, S receptor binding domain (RBD), and SARS-CoV-2 neutralizing antibodies in both vaccination protocols. Overall, we found very comparable immune responses following short- or long-interval immunization. Thus, our results suggest that the chosen time intervals may not be suitable to observe potential differences in antigen-specific immunity when testing different prime-boost intervals with our candidate vaccines in the mouse model. Despite this, our data clearly showed that MVA-SARS-2-ST induced superior humoral immune responses relative to MVA-SARS-2-S after both immunization schedules.

Waning cellular immune responses and predictive factors in maintaining cellular immunity against SARS-CoV-2 six months after BNT162b2 mRNA vaccination.

Several clinical trials have shown that the humoral response produced by anti-spike antibodies elicited by coronavirus disease 2019 (COVID-19) vaccines gradually declines. The kinetics, durability and influence of epidemiological and clinical factors on cellular immunity have not been fully elucidated. We analyzed cellular immune responses elicited by BNT162b2 mRNA vaccines in 321 health care workers using whole blood interferon-gamma (IFN-γ) release assays. IFN-γ, induced by CD4 + and CD8 + T cells stimulated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike epitopes (Ag2), levels were highest at 3 weeks after the second vaccination (6 W) and decreased by 37.4% at 3 months (4 M) and 60.0% at 6 months (7 M), the decline of which seemed slower than that of anti-spike antibody levels. Multiple regression analysis revealed that the levels of IFN-γ induced by Ag2 at 7 M were significantly correlated with age, dyslipidemia, focal adverse reactions to full vaccination, lymphocyte and monocyte counts in whole blood, Ag2 levels before the second vaccination, and Ag2 levels at 6 W. We clarified the dynamics and predictive factors for the long-lasting effects of cellular immune responses. The results emphasize the need for a booster vaccine from the perspective of SARS-CoV-2 vaccine-elicited cellular immunity.

COVID-19: The Course, Vaccination and Immune Response in People with Multiple Sclerosis: Systematic Review.

When the Coronavirus Disease 2019 (COVID-19) appeared, it was unknown what impact it would have on the condition of patients with autoimmunological disorders. Attention was focused on the course of infection in patients suffering from multiple sclerosis (MS), specially treated with disease-modifying therapies (DMTs) or glucocorticoids. The impact of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection on the occurrence of MS relapses or pseudo-relapses was important. This review focuses on the risk, symptoms, course, and mortality of COVID-19 as well as immune response to vaccinations against COVID-19 in patients with MS (PwMS). We searched the PubMed database according to specific criteria. PwMS have the risk of infection, hospitalization, symptoms, and mortality due to COVID-19, mostly similar to the general population. The presence of comorbidities, male sex, a higher degree of disability, and older age increase the frequency and severity of the COVID-19 course in PwMS. For example, it was reported that anti-CD20 therapy is probably associated with an increased risk of severe COVID-19 outcomes. After SARS-CoV-2 infection or vaccination, MS patients acquire humoral and cellular immunity, but the degree of immune response depends on applied DMTs. Additional studies are necessary to corroborate these findings. However, indisputably, some PwMS need special attention within the context of COVID-19.

GRAd-COV2 vaccine provides potent and durable humoral and cellular immunity to SARS-CoV-2 in randomized placebo-controlled phase 2 trial.

The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic and heterologous immunization approaches implemented worldwide for booster doses call for diversified vaccine portfolios. GRAd-COV2 is a gorilla adenovirus-based COVID-19 vaccine candidate encoding prefusion-stabilized spike. The safety and immunogenicity of GRAd-COV2 is evaluated in a dose- and regimen-finding phase 2 trial (COVITAR study, ClinicalTrials.gov: NCT04791423) whereby 917 eligible participants are randomized to receive a single intramuscular GRAd-COV2 administration followed by placebo, or two vaccine injections, or two doses of placebo, spaced over 3 weeks. Here, we report that GRAd-COV2 is well tolerated and induces robust immune responses after a single immunization; a second administration increases binding and neutralizing antibody titers. Potent, variant of concern (VOC) cross-reactive spike-specific T cell response peaks after the first dose and is characterized by high frequencies of CD8s. T cells maintain immediate effector functions and high proliferative potential over time. Thus, GRAd vector is a valuable platform for genetic vaccine development, especially when robust CD8 response is needed.

Obesity and immune status in children.

PURPOSE OF REVIEW: Childhood obesity, with persistent chronic inflammation, is a worldwide epidemic. Obesity causes dysregulation throughout the immune system, affecting the balance and levels of cytokines, adipokines, and innate and adaptive immune cells. The present review focuses on the impact of obesity on immune function in children: altering the baseline activation state of immune cells and affecting the ability of the host to combat pathogens and malignancy and respond appropriately to vaccination. RECENT FINDINGS: Obesity causes dysregulation of the immune system. Single-cell RNA-sequencing of adipose tissue and resident immune cells is quantifying the impact of obesity on the frequency of immune cell subsets and their states. The system-wide alterations in immune function in obesity are most evident upon perturbation, including the response to infection (e.g. increased risk of severe COVID-19 in the ongoing pandemic), vaccination, and malignancy. However, mechanistic research in pediatric obesity is limited and this impacts our ability to care for these children. SUMMARY: We must better understand baseline and perturbed immune health in obese children to determine how to account for altered frequency and function of humoral and cellular immune components in acute infection, during vaccine design and when considering therapeutic options for this complex, medically vulnerable group.

SARS-CoV-2 vaccine-induced humoral and cellular immunity in patients with hematologic malignancies.

Patients with hematologic conditions have a higher risk of severe COVID-19 and COVID-19-related death. This is related to immune deficiencies induced by hematologic conditions and/or the treatment thereof. Prospective vaccine immunogenicity studies have demonstrated that in the majority of patients, a 3-dose COVID-19 vaccination schedule leads to antibody concentrations comparable to levels obtained in healthy adults after a 2-dose schedule. In B cell depleted patients, humoral responses are poor, however vaccination did induce potent cellular immune responses. The effect of 3-dose vaccination schedules and COVID-19 booster vaccinations on the protection of patients with hematologic malignancies against severe COVID-19 and COVID-19 related death remains to be confirmed by population-based vaccine effectiveness studies.

The effects of methotrexate on the immune responses to the COVID-19 vaccines in the patients with immune-mediated inflammatory disease: A systematic review of clinical evidence.

COVID-19 vaccines exhibit high levels of immunogenicity in the overall population. Data on the effects of immunomodulators on the consequences of COVID-19 in patients with Immune-mediated inflammatory diseases (IMIDs) remains scarce. This systematic review aimed to evaluate the immune responses to the COVID-19 vaccines in IMID patients receiving methotrexate (MTX) compared to healthy individuals. A comprehensive literature search was carried out using electronic databases such as PubMed, Web of Science, Scopus, Google Scholar, and Embase up to August 2022 to identify eligible RCTs evaluating the effect of MTX on immune responses in patients with COVID-19. The PRISMA checklist protocol was applied for the quality assessment of the selected trials. Our findings demonstrated that MTX lowered the responses of T cells and antibodies in IMID patients compared to healthy controls. We also discovered that young age (<60 years) was the main parameter influencing the antibody response after vaccination, while MTX had little effect. Following vaccination, MTX-hold and age were considered the main factors influencing the antibody response. In patients older than 60 years of age, the time point of 10 days of MTX discontinuation was critical to boosting the humoral response to anti-SARS-CoV-2 IgG. Because many IMID patients did not have adequate humoral and cellular responses, our findings highlighted the importance of second or booster doses of vaccine and temporary MTX discontinuation. As a result, it implies that individuals with IMIDs should be subjected to more research, particularly humoral and cellular immunity efficiency trials after COVID-19 vaccination, until credible information is achieved.

Blood unconjugated bilirubin and tacrolimus are negative predictors of specific cellular immunity in kidney transplant recipients after SAR-CoV-2 inactivated vaccination.

The immunogenicity of SARS-CoV-2 vaccines is poor in kidney transplant recipients (KTRs). The factors related to poor immunogenicity to vaccination in KTRs are not well defined. Here, observational study demonstrated no severe adverse effects were observed in KTRs and healthy participants (HPs) after first or second dose of SARS-CoV-2 inactivated vaccine. Different from HPs with excellent immunity against SARS-CoV-2, IgG antibodies against S1 subunit of spike protein, receptor-binding domain, and nucleocapsid protein were not effectively induced in a majority of KTRs after the second dose of inactivated vaccine. Specific T cell immunity response was detectable in 40% KTRs after the second dose of inactivated vaccine. KTRs who developed specific T cell immunity were more likely to be female, and have lower levels of total bilirubin, unconjugated bilirubin, and blood tacrolimus concentrations. Multivariate logistic regression analysis found that blood unconjugated bilirubin and tacrolimus concentration were significantly negatively associated with SARS-CoV-2 specific T cell immunity response in KTRs. Altogether, these data suggest compared to humoral immunity, SARS-CoV-2 specific T cell immunity response are more likely to be induced in KTRs after administration of inactivated vaccine. Reduction of unconjugated bilirubin and tacrolimus concentration might benefit specific cellular immunity response in KTRs following vaccination.

Determinants of humoral and cellular immune responses to three doses of mRNA SARS-CoV-2 vaccines in older adults: a longitudinal cohort study.

BACKGROUND: Older age is associated with poorer outcomes to COVID-19 infection. The Norwegian Institute of Public Health established a longitudinal cohort of adults aged 65-80 years to study the effects of the COVID-19 pandemic. Here we describe the characteristics of the cohort in general, and specifically the immune responses at baseline and after primary and booster vaccination in a subset of longitudinal blood samples, and the epidemiological factors affecting these responses. METHODS: 4551 participants were recruited, with humoral (n=299) and cellular (n=90) responses measured before vaccination and after two and three vaccine doses. Information on general health, infections, and vaccinations were obtained from questionnaires and national health registries. FINDINGS: Half of the participants had a chronic condition. 849 (18·7%) of 4551 were prefrail and 184 (4%) of 4551 were frail. 483 (10·6%) of 4551 had general activity limitations (scored with the Global Activity Limitation Index). After dose two, 295 (98·7%) of 299 participants were seropositive for anti-receptor binding domain IgG, and 210 (100%) of 210 participants after dose three. Spike-specific CD4 and CD8 T cell responses showed high heterogeneity after vaccination and responded to the alpha (B.1.1.7), delta (B.1.617.2), and omicron (B.1.1.529 or BA.1) variants of concern. Cellular responses to seasonal coronaviruses increased after SARS-CoV-2 vaccination. Heterologous prime boosting with mRNA vaccines was associated with the highest antibody (p=0·019) and CD4 T cell responses (p=0·003), and hypertension with lower antibody levels after three doses (p=0·04). INTERPRETATION: Most older adults, including those with comorbidities, generated good serological and cellular responses after two vaccine doses. Responses further improved after three doses, particularly after heterologous boosting. Vaccination also generated cross-reactive T cells against variants of concern and seasonal coronaviruses. Frailty was not associated with impaired immune responses, but hypertension might indicate reduced responsiveness to vaccines even after three doses. Individual differences identified through longitudinal sampling enables better prediction of the variability of vaccine responses, which can help guide future policy on the need for subsequent doses and their timing. FUNDING: Norwegian Institute of Public Health, Norwegian Ministry of Health, Research Council of Norway, and Coalition for Epidemic Preparedness Innovations.

Cellular immunity in COVID-19 and other infections in Common variable immunodeficiency.

COVID-19 has shed light on the role of cellular immunity in the absence of humoral response in different patient groups. Common variable immunodeficiency (CVID) is characterized by impaired humoral immunity but also an underlying T-cell dysregulation. The impact of T-cell dysregulation on cellular immunity in CVID is not clear, and this review summarizes available literature on cellular immunity in CVID with a particular focus on COVID-19. Overall mortality of COVID-19 in CVID is difficult to assess, but seems not significantly elevated, and risk factors for severe disease mirrors that of the general population, including lymphopenia. Most CVID patients have a significant T-cell response to COVID-19 disease with possible cross-reactivity to endemic coronaviruses. Several studies find a significant but impaired cellular response to basal COVID-19 mRNA vaccination that is independent of an antibody response. CVID patients with infection only have better cellular responses to vaccine in one study, but there is no clear association to T-cell dysregulation. Cellular response wane over time but responds to a third booster dose of vaccine. Opportunistic infection as a sign of impaired cellular immunity in CVID is rare but is related to the definition of the disease. CVID patients have a cellular response to influenza vaccine that in most studies is comparable to healthy controls, and annual vaccination against seasonal influenza should be recommended. More research is required to clarify the effect of vaccines in CVID with the most immediate issue being when to booster the COVID-19 vaccine.

Flow cytometry profiling of cellular immune response in COVID-19 infected, recovered and vaccinated individuals.

INTRODUCTION: SARS-CoV-2 has infected over 753 million individuals and caused more than 6.8 million deaths globally to date. COVID-19 disease severity has been associated with SARS-CoV-2 induced hyper inflammation and the immune correlation with its pathogenesis remains unclear. Acute viral infection is characterised by vigorous coordinated innate and adaptive activation, including an early cellular response that correlates well with the amplitude of virus specific humoral response. OBJECTIVE: The present study covers a wide spectrum of cellular immune response against COVID-19, irrespective of infection and vaccination. METHODS: We analysed immune status of (a) COVID-19 hospitalised patients including deceased and recovered patients, and compared with home isolated and non-infected healthy individuals, and (b) infected home isolated individuals with vaccinated individuals, using flow cytometry. We performed flow cytometry analysis of PBMCs to determine non-specific cell-mediated immune response. RESULTS: The immune response revealed extensive induction and activation of multiple immune lineages, including T and B cells, Th17 regulatory subsets and M1, M2 macrophages in deceased and hospitalised recovered patients, vaccinated and healthy individuals. Compromised immune cell expression was observed in deceased patients even in later stages, while expression was restored in hospitalised recovered patients and home isolated individuals. CONCLUSION: The findings associated with recovery and convalescence define a new signature of cellular immune response that persists in individuals with SARS-CoV-2 infection and vaccination. The findings will help in providing a better understanding of COVID-19 disease and will aid in developing better therapeutic strategies for treatment.

Longitudinal humoral and cell-mediated immune responses in a population-based cohort in Zurich, Switzerland between March and June 2022 - evidence for protection against Omicron SARS-CoV-2 infection by neutralizing antibodies and spike-specific T-cell responses.

OBJECTIVES: The correlate(s) of protection against SARS-CoV-2 remain incompletely defined. Additional information regarding the combinations of antibody and T cell-mediated immunity which can protect against (re)infection is needed. METHODS: We conducted a population-based, longitudinal cohort study including 1044 individuals of varying SARS-CoV-2 vaccination and infection statuses. We assessed spike (S)- and nucleocapsid (N)-immunoglobulin(Ig)G and wildtype, Delta, and Omicron-neutralizing antibody (N-Ab) activity. In a subset of 328 individuals, we evaluated S, membrane (M), and N-specific T cells. Three months later, we reassessed Ab (n = 964) and T cell (n = 141) responses and evaluated factors associated with protection from (re)infection. RESULTS: At the study start, >98% of participants were S-IgG seropositive. N-IgG and M/N-T-cell responses increased over time, indicating viral (re)exposure, despite existing S-IgG. Compared to N-IgG, M/N-T cells were a more sensitive measure of viral exposure. High N-IgG titers, Omicron-N-Ab activity, and S-specific-T-cell responses were all associated with a reduced likelihood of (re)infection over time. CONCLUSION: Population-level SARS-CoV-2 immunity is S-IgG-dominated, but heterogeneous. M/N-T-cell responses can distinguish previous infection from vaccination, and monitoring a combination of N-IgG, Omicron-N-Ab, and S-T-cell responses may help estimate protection against SARS-CoV-2 (re)infection.

Cellular Immune Responses to SARS-CoV-2 in Exposed Seronegative Individuals.

Some SARS-CoV-2-exposed individuals develop immunity without overt infection. We identified 11 individuals who were negative by nucleic acid testing during prolonged close contact and with no serological diagnosis of infection. As this could reflect natural immunity, cross-reactive immunity from previous coronavirus exposure, abortive infection due to de novo immune responses, or other factors, our objective was to characterize immunity against SARS-CoV-2 in these individuals. Blood was processed into plasma and peripheral blood mononuclear cells (PBMC) and screened for IgG, IgA, and IgM antibodies (Ab) against SARS-CoV-2 and common ß-coronaviruses OC43 and HKU1. Receptor blocking activity and interferon-alpha (IFN-α) in plasma were also measured. Circulating T cells against SARS-CoV-2 were enumerated and CD4+ and CD8+ T cell responses discriminated after in vitro stimulation. Exposed uninfected individuals were seronegative against SARS-CoV-2 spike (S) and selectively reactive against OC43 nucleocapsid protein (N), suggesting common ß-coronavirus exposure induced Ab cross-reactive against SARS-CoV-2 N. There was no evidence of protection from circulating angiotensin-converting enzyme (ACE2) or IFN-α. Six individuals had T cell responses against SARS-CoV-2, with four involving CD4+ and CD8+ T cells. We found no evidence of protection from SARS-CoV-2 through innate immunity or immunity induced by common ß-coronaviruses. Cellular immune responses against SARS-CoV-2 were associated with time since exposure, suggesting that rapid cellular responses may contain SARS-CoV-2 infection below the thresholds required for a humoral response.

Toward a pan-SARS-CoV-2 vaccine targeting conserved epitopes on spike and non-spike proteins for potent, broad and durable immune responses.

BACKGROUND: The SARS-CoV-2 non-Spike (S) structural protein targets on nucleocapsid (N), membrane (M) and envelope (E), critical in the host cell interferon response and memory T-cell immunity, are grossly overlooked in COVID vaccine development. The current Spike-only vaccines bear an intrinsic shortfall for promotion of a fuller T cell immunity. Vaccines designed to target conserved epitopes could elicit strong cellular immune responses that would synergize with B cell responses and lead to long-term vaccine success. We pursue a universal (pan-SARS-CoV-2) vaccine against Delta, Omicrons and ever-emergent new mutants. METHODS AND FINDINGS: We explored booster immunogenicity of UB-612, a multitope-vaccine that contains S1-RBD-sFc protein and sequence-conserved promiscuous Th and CTL epitope peptides on the Sarbecovirus N, M and S2 proteins. To a subpopulation (N = 1,478) of infection-free participants (aged 18-85 years) involved in a two-dose Phase-2 trial, a UB-612 booster (third dose) was administered 6-8 months after the second dose. The immunogenicity was evaluated at 14 days post-booster with overall safety monitored until the end of study. The booster induced high viral-neutralizing antibodies against live Wuhan WT (VNT50, 1,711) and Delta (VNT50, 1,282); and against pseudovirus WT (pVNT50, 11,167) vs. Omicron BA.1/BA.2/BA.5 variants (pVNT50, 2,314/1,890/854), respectively. The lower primary neutralizing antibodies in the elderly were uplifted upon boosting to approximately the same high level in young adults. UB-612 also induced potent, durable Th1-oriented (IFN-γ+-) responses (peak/pre-boost/post-boost SFU/106 PBMCs, 374/261/444) along with robust presence of cytotoxic CD8+ T cells (peak/pre-boost/post-boost CD107a+-Granzyme B+, 3.6%/1.8%/1.8%). This UB-612 booster vaccination is safe and well tolerated without SAEs. CONCLUSIONS: By targeting conserved epitopes on viral S2, M and N proteins, UB-612 could provide potent, broad and long-lasting B-cell and T-cell memory immunity and offers the potential as a universal vaccine to fend off Omicrons and new VoCs without resorting to Omicron-specific immunogens. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT04773067; ClinicalTrials.gov ID: NCT05293665; ClinicalTrials.gov ID: NCT05541861.

Humoral and cellular immune response to second and third severe acute respiratory syndrome coronavirus 2 mRNA vaccine in patients with plasma cell dyscrasia.

BACKGROUND: The recently developed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccine has a short history of use and further information is needed regarding its efficacy, especially in immunocompromised conditions, such as plasma cell dyscrasia (PCD). METHODS: We retrospectively measured serum SARS-CoV-2 antibodies against the spike protein (S-IgG) after the second and third mRNA vaccine doses (doses 2 and 3, respectively) in 109 patients with PCD. We evaluated the proportion of patients with an adequate humoral response (defined as S-IgG titers ≥300 antibody units/mL). RESULTS: Although active anti-myeloma treatments prior to vaccination had a significantly negative impact on adequate humoral response, specific drug subclasses including immunomodulatory drugs, proteasome inhibitors, and monoclonal antibodies were not negatively associated, except for B-cell maturation antigen-targeted therapy. Dose 3 (booster vaccination) led to significantly higher S-IgG titers and more patients acquired an adequate humoral response. Furthermore, evaluation of vaccine-induced cellular immune response in patients using T-spot Discovery SARS-CoV-2 kit, revealed an enhanced cellular immune response after Dose 3. CONCLUSIONS: This study highlighted the significance of booster SARS-CoV-2 mRNA vaccination in patients with PCD with respect to humoral and cellular immunity. Moreover, this study highlighted the potential impact of certain drug subclasses on vaccine-induced humoral immune response.

Third SARS-CoV-2 vaccination and breakthrough infections enhance humoral and cellular immunity against variants of concern.

Introduction: SARS-CoV-2 vaccination is the leading strategy to prevent severe courses after SARS-CoV-2 infection. In our study, we analyzed humoral and cellular immune responses in detail to three consecutive homologous or heterologous SARS-CoV-2 vaccinations and breakthrough infections. Methods: Peripheral blood samples of n=20 individuals were analyzed in the time course of three SARS-CoV-2 vaccinations and/or breakthrough infection. S1-, RBD-, S2- and N-specific IgG antibodies were quantified using Luminex-based multiplex assays and electrochemiluminescence multiplex assays for surrogate neutralization in plasma. Changes in cellular immune components were determined via flow cytometry of whole blood samples. Results: All individuals (n=20) responded to vaccination with increasing S1-/RBD-/S2-specific IgG levels, whereas specific plasma IgA displayed individual variability. The third dose increased antibody inhibitory capacity (AIC) against immune-escape variants Beta and Omicron BA.1 independently of age. The mRNA-primed vaccination induced IgG and IgA immunity more efficiently, whereas vector-primed individuals displayed higher levels of memory T and B cells. Vaccinees showed SARS-CoV-2-specific T cell responses, which were further improved and specified after Omicron breakthrough infections in parallel to the appearance of new variant-specific antibodies. Discussion: In conclusion, the third vaccination was essential to increase IgG levels, mandatory to boost AIC against immune-escape variants, and induced SARS-CoV-2-specific T cells. Breakthrough infection with Omicron generates additional spike specificities covering all known variants.