Vaccine Arm Research Articles

A randomized phase 2 study of an individualized neoantigen-targeting immunotherapy in patients with newly diagnosed metastatic microsatellite stable colorectal cancer (MSS-CRC).

LBA13 Background: Neoantigen-targeting immunotherapy aims to provide therapeutic benefit to patients by generating potent neoantigen-specific T cells. GRANITE is an immunotherapy regimen that uses chimpanzee adenovirus and self-amplifying mRNA vaccines encoding patient-specific neoantigens in combination with immune checkpoint inhibitors. Preliminary efficacy was noted in MSS-CRC (Palmer et al Nature Medicine 2022) and this regimen is being assessed in a randomized Phase 2 study in 1L metastatic MSS-CRC (NCT05141721). Methods: Patients (pts) with 20 neoantigens based on the EDGEÔ prediction model were randomized 1:1 to receive the GRANITE regimen in addition to 1L standard of care (SOC) (GRANITE vaccine arm), or 1L SOC alone (control arm). Results: Baseline demographics and disease characteristics were balanced between arms. As of 15 Oct 2024, GRANITE pts had an improvement in PFS relative to control pts (HR=0.73, 90% CI [0.44, 1.21]). In this study, high and low disease burden groups were identified using baseline ctDNA assessed by Gritstone’s validated, highly sensitive, tumor-informed assay. Patients with low disease burden benefited more than those with high disease burden, consistent with emerging data suggesting neoantigen-targeting immunotherapy having greater activity in minimal disease settings (e.g., adjuvant setting). Furthermore, in the low disease burden group at the most recent study visit, more patients were free of progression with very low ctDNA levels (ie, below the limit of quantification of the assay) in the GRANITE arm, 41% (7/17), versus the control arm, 21% (3/14). The greater proportion of GRANITE patients both free of progression and with very low ctDNA, suggests potential further separation of PFS cuves with additional follow up. Neoantigen-specific T cell responses were observed in 100% of patients in the GRANITE arm with evaluable PBMC samples (17/17 assessed by ex vivo and in vitro stimulation ELISpots). Molecular responses based on a reduction in ctDNA at a single timepoint was similar between arms (39% in GRANITE and 40% in control arms). Most common (≥20%) treatment-related adverse events (TRAE) included pyrexia and influenza like illness and no pts discontinued due to a TRAE. Conclusion: This randomized study shows GRANITE may benefit patients, especially those with low burden disease, in this front line setting of metastatic MSS-CRC that has not benefitted from immunotherapy. Updated analysis will be presented. Clinical trial information: NCT05141721 .

P-42. Systematic review and meta-analysis of recombinant herpes zoster vaccine in immunocompromised populations

Abstract Background Herpes zoster infection is common in immunocompromised individuals. Recently, the Advisory Committee on Immunization Practices recommended immunizing with the recombinant zoster vaccine (RZV). Methods Objective: To evaluate the efficacy, immunogenicity and safety of RZV in immunocompromised individuals, such as transplant recipients, cancer patients undergoing chemotherapy, individuals with preexisting autoimmune diseases and HIV-infected patients. Data Sources and Study Selection: From January 1984 to October 2023, a systematic search of PubMed, MEDLINE, EMBASE, Scopus, Web of Science, CINAHL, and Cochrane CENTRAL was performed. Randomized clinical trials (RCT) evaluating RZV compared to placebo in immunocompromised adults were selected. Data Extraction and Synthesis: Study characteristics and estimates on the incidence of herpes zoster, humoral and cellular immune responses, and safety data were extracted from studies. Estimates were pooled using random-effects meta-analysis. Differences by study-level characteristics were estimated using subgroup meta-analysis and metaregression. Results Seven RCTs were included. Compared to placebo, RZV reduced the incidence of herpes zoster across all ages by 81% (RR: 0.19, 95%CI: 0.09, 0.44), with moderate heterogeneity across the studies (I2 = 60.49%; τ2 = 0.31; P=0.07). RZV significantly increased humoral and cellular immunity one month after the last dose. Transplant and past malignancy were associated with lower immunogenicity. RZV was more reactogenic with more local and systemic adverse events. There was no difference in serious adverse events or death between the vaccine and placebo arms. Conclusion This study suggests that RZV reduces the risk of herpes zoster infection in immunocompromised individuals. This vaccine should be routinely offered to immunocompromised individuals, preferably before chemotherapy or treatment. Disclosures All Authors: No reported disclosures

BIOS-05. PEPTIDE-BASED VACCINES VERSUS DENDRITIC CELL-BASED VACCINE THERAPIES FOR PATIENTS WITH GLIOBLASTOMA: A NETWORK META-ANALYSIS OF CONTROLLED CLINICAL TRIALS

Abstract BACKGROUND Glioblastoma (GBM) is the most prevalent primary CNS malignancy in adults, often with a bleak prognosis. Reports suggest the efficacy of dendritic cell vaccines (DCV) and peptide vaccines in extending overall survival (OS). We aimed to compare their efficacy using network meta-analysis (NMA). METHODS We systematically searched PubMed, Cochrane database, SCOPUS, and Clinicaltrials.gov up to February 2024 for controlled trials on DCV or peptide vaccines for GBM. NMA was conducted using the frequentist approach to obtain direct and indirect comparisons of each vaccine. Pairwise analyses were performed using the inverse variance method, comparing each vaccine’s efficacy. PEPvIII-KLH and Rindopepimut were merged into “Peptide-based vaccines” [PEP], and standard of care (SOC) and (Placebo + SOC) were merged. Primary outcome: hazard ratio (HR) of overall survival with 95% confidence intervals. RESULTS Analysis included 5 studies with 451 patients (vaccine arm) and 445 controls, with SOC/[Placebo + SOC] as reference. Common effects model showed DCV + SOC significantly reduced the HR to 0.3385 [0.1753; 0.6539], while the peptide-based vaccine + SOC reduced the HR to 0.8276 [0.6960; 0.9840]. In the random effects model, DCV + SOC had an HR of 0.3132 [0.0839; 1.1688], and the peptide-based vaccine + SOC had an HR of 0.3888 [0.1383; 1.0928]. Heterogeneity: tau^2 = 0.6473, tau = 0.8045, I^2 = 77.7% [39.5%; 91.8%]. In a pairwise meta-analysis comparing the DCV+SOC and SOC/[Placebo + SOC] consisting of 2 trials, the common and random effects models both estimated an HR of 0.3385 [0.1753; 0.6539, I^2 = 0.0%]. Comparing the PEP+SOC and SOC/[Placebo + SOC] based on 3 trials, the common effect model estimated an HR of 0.8276 [0.6960; 0.9840], while the random effects model estimated an HR of 0.3874 [0.1360; 1.1039, I^2 = 84.4%]. CONCLUSION Based on current evidence, DCV vaccines perform better than peptide-based vaccines in reducing mortality in GBM patients. Further trials are required to validate their efficacies.

A Phase II/III multicenter randomized single blind non-inferiority immunogenicity and safety study of TeddyVac™ vaccine of Human Biologicals Institute in healthy subjects of 10 years to 60 years of age

Background WHO and other health agencies recommend that tetanus toxoid (TT) should be replaced by tetanus-diphtheria (Td) vaccine taking into consideration the low coverage and waning immunity, especially for diphtheria. In this randomised, multicentre, non-inferiority study, the immunogenicity and safety of TeddyVac™ vaccine of Human Biologicals Institute were compared with an existing brand. Methods The study involved 444 eligible subjects in two age groups at four centres across India. Group A included subjects of 18–60 years and Group B subjects of 10–18 years of age. All subjects received single dose of either TeddyVac™ or the comparator vaccine as per randomisation. Blood samples for antibody titre estimation were collected before vaccination and 4–6 weeks after vaccination. Immunogenicity was assessed by estimating seroconversion rate, seroprotection rate, and geometric mean titres of antibodies. Safety was evaluated by collection and analysis of data on solicited and unsolicited adverse events. Results Overall, 441 subjects completed the study. Both the vaccine arms showed comparable seroconversion after a single dose for both the components. Both arms showed increase in seroprotection and geometric mean titres after a single dose of vaccination for both vaccine components, being significantly better for the diphtheria component in the test vaccine arm. Only few minor local and systemic adverse events were observed in both the vaccine arms. No serious adverse event was reported. Conclusion The study results indicate that the TeddyVac™ vaccine is immunogenic, safe and non-inferior to the comparator Vaccine when administered to healthy subjects of 10 to 60 years of age. CTRI Registration number CTRI/2021/07/035112

Phase II Trial of HER-Vaxx, a B-cell Peptide-Based Vaccine, in HER2-Overexpressing Advanced Gastric Cancer Patients Under Platinum-Based Chemotherapy (HERIZON).

A multicenter, randomized, open-label, phase II study (HERIZON; NCT02795988) was conducted to evaluate the clinical and immunologic efficacy of HER-Vaxx (IMU-131), a B-cell, peptide-based vaccine targeting HER2 overexpressed in 6% to 30% of gastroesophageal adenocarcinomas (GEA). Patients (n = 36) with GEA were treated with standard-of-care chemotherapy (n = 17) or HER-Vaxx plus chemotherapy (n = 19), using the recommended phase 2 dose for the vaccine. Overall survival (OS; primary endpoint), safety, progression-free survival (PFS), clinical response (secondary endpoints), and vaccine-induced HER2-specific antibody levels in serum and correlation with tumor response rates (exploratory endpoints) were investigated. A 40% OS benefit [HR, 0.60; median OS, 13.9 months; 80% confidence interval (CI), 7.52-14.32] for patients treated with HER-Vaxx plus chemotherapy compared with OS of 8.31 months (80% CI, 6.01-9.59) in patients that received chemotherapy alone. A 20% PFS difference was obtained for the vaccination arm (HR, 0.80; 80% CI, 0.47, 1.38). No additional toxicity due to HER-Vaxx was observed. The vaccine-induced high levels of HER2-specific total IgG and IgG1 antibodies (P < 0.001 vs. controls) that significantly correlated with tumor reduction (IgG, P = 0.001; IgG1, P = 0.016), had a significant capacity in inhibiting phosphorylation of the intracellular HER2-signaling pathways, mediated antibody-dependent cellular cytotoxicity, and decreased immunosuppressive FOXP3+ regulatory T cells. HER-Vaxx plus standard chemotherapy exhibits an excellent safety profile and improves OS. Furthermore, vaccine-induced immune response was significantly associated with reduced tumor size compared with standard-of-care chemotherapy. The presented vaccination approach may substitute for treatment with trastuzumab, upon unavailability or toxicity, based on further evidence of equivalent treatment efficacy.

Randomized controlled trial reveals no benefit to a 3-month delay in COVID-19 mRNA booster vaccine.

BACKGROUNDThere is uncertainty about the timing of booster vaccination against COVID-19 in highly vaccinated populations during the present endemic phase of COVID-19. Studies focused on primary vaccination have previously suggested improved immunity with a longer interval between the first and second vaccine doses.METHODSWe conducted a randomized, controlled trial (November 2022-August 2023) and assigned 52 fully vaccinated adults to an immediate or a 3-month delayed bivalent Spikevax mRNA booster vaccine. Follow-up visits were completed for 48 participants (n = 24 per arm), with collection of saliva and plasma samples following each visit.RESULTSThe rise in neutralizing antibody responses to ancestral and Omicron strains were almost identical between the immediate and delayed vaccination arms. Analyses of plasma and salivary antibody responses (IgG, IgA), plasma antibody-dependent phagocytic activity, and the decay kinetics of antibody responses were similar between the 2 arms. Symptomatic and asymptomatic SARS-CoV-2 infections occurred in 49% (21 of 49) participants over the median 11.5 months of follow-up and were also similar between the 2 arms.CONCLUSIONSOur data suggest that there was no benefit in delaying COVID-19 mRNA booster vaccination in preimmune populations during the present endemic phase of COVID-19.TRIAL REGISTRATIONAustralian New Zealand Clinical Trials Registry number 12622000411741 (https://anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12622000411741).FUNDINGNational Health and Medical Research Council, Australia (program grant App1149990) and Medical Research Future Fund (App2005544).

A first-in-human study to evaluate a personalized neoantigen-based mRNA-loaded dendritic cell vaccine, in combination with ablation, in patients with hepatocellular carcinoma.

e14513 Background: Local recurrence of Hepatocellular Carcinoma (HCC) following potentially curative resection or ablation is an inevitable risk. T cells recognizing neoantigens are present in most cancers including HCC and offer a specific and highly immunogenic target for the personalized vaccination as an adjuvant therapy. The purpose of this study is to evaluate the safety and T cell immune response of a personalized neoantigen-based mRNA loaded dendritic cell (DC) vaccine (LK101) combined with regular ablation in patients with HCC (NCT03674073). Methods: Each patient’s fresh tumor biopsy and matched peripheral blood sample were subjected to whole-exome sequencing and RNA-sequencing. Following determination of somatic mutations and gene expression, up to 30 in silico–predicted potential neoantigens were selected with bioinformatic tool. DCs were generated from the monocytes enriched by leukapheresis, followed by transfection with neoantigen-encoding mRNA through electroporation. In total, 7 doses of LK101 were administered at 1.5×107 cells/injection intradermally with 4-dose priming weekly and 3 boosters in 4-week intervals. The primary endpoint of the clinical study was safety, and key secondary endpoints were immunogenicity, overall survival and recurrence. 24 HCC patients at HKLC stage IIa were enrolled 1:1 to ablation control arm and ablation combined with DC (LK101) arm. Results: The study was completed, patients were followed up for a median of 48.4 months and 38.8 months in vaccination arm and control arm. All of adverse events were Grade 1-2. Most frequent treatment-related adverse events are injection site reactions, inclusive of local pain (63.6%), itch (27.3%) and others (27.3%), such as redness and edema. 3 patients in ablation control arm died, whereas all vaccinated patients survived. The 1-year and 2-year recurrence rates in vaccination arm compared with control arm are 18.2%, respectively. LK101 induced neoantigen-specific T cell responses were investigated by ELISpot analysis. Overall, all patients elicited at least one measurable response. Immune responses to 60-90% of neoantigen peptides were seen post vaccination across patients. Both preexisting immune response and De Novo immune response that targeted neoantigens were observed in vaccinated patients. Moreover, both CD4 and CD8 positive effector memory T cells showed the trend of increase, and PD-1 positive T cells reduced in peripheral blood of patients after vaccination. Conclusions: Combination of LK101 with ablation therapy has a manageable safety profile, showing the evidence of immune activation and potential of prolonged survival. In combination with regular ablation, neoantigen based mRNA loaded DC vaccine is a promising immunotherapy for the treatment of HCC. Clinical trial information: NCT03674073 .

Mediation analyses for the effect of antibodies in vaccination

Abstract We review standard mediation assumptions as they apply to identifying antibody effects in a randomized vaccine trial and propose new study designs to allow the identification of an estimand that was previously unidentifiable. For these mediation analyses, we partition the total ratio effect (one minus the vaccine effect) from a randomized vaccine trial into indirect (effects through antibodies) and direct effects (other effects). Identifying λ \lambda , the proportion of the total effect due to an indirect effect, depends on a cross-world quantity, the potential outcome among vaccinated individuals with antibody levels as if given placebo, or vice versa. We review assumptions for identifying λ \lambda and show that there are two versions of λ \lambda , unless the effect of adding antibodies to the placebo arm is equal in magnitude to the effect of subtracting antibodies from the vaccine arm. We focus on the case when individuals in the placebo arm are unlikely to have the needed antibodies. In that case, if a standard assumption (given confounders the potential mediators and potential outcomes are independent) is true, only one version of λ \lambda is identifiable, and if not neither is identifiable. We propose alternatives for identifying the other version of λ \lambda , using experimental design to identify a formerly cross-world quantity. Two alternative experimental designs use a three-arm trial with the extra arm being passive immunization (administering monoclonal antibodies), with or without closeout vaccination. Another alternative is to combine information from a placebo-controlled vaccine trial with a placebo-controlled passive immunization trial.

Multipeptide vaccines for melanoma in the adjuvant setting: long-term survival outcomes and post-hoc analysis of a randomized phase II trial

The critical roles of CD4+ T cells have been understudied for cancer vaccines. Here we report long-term clinical outcomes of a randomized multicenter phase II clinical trial (NCT00118274), where patients with high-risk melanoma received a multipeptide vaccine targeting CD8+ T cells (12MP) and were randomized to receive either of two vaccines for CD4+ (helper) T cells: 6MHP (6 melanoma-specific helper peptides), or tet (a nonspecific helper peptide from tetanus toxoid). Cyclophosphamide (Cy) pre-treatment was also assessed. Primary outcomes for T cell responses to 12MP, 6MHP, and tet were previously reported, suggesting immunogenicity of both vaccines but that CD8 T cell responses to 12MP were lower when tet was replaced with 6MHP. Here, in post-hoc analyses, we report durable prolongation of overall survival by adding 6MHP instead of tet. That benefit was experienced only by male patients. A favorable interaction of 6MHP and Cy is also suggested. Multivariable Cox regression analysis of the intent-to-treat population identify vaccine arm (12MP + 6MHP+Cy) and patient sex (male) as the two significant predictors of enhanced survival. These findings support the value of adding cognate T cell help to cancer vaccines and also suggest a need to assess the impact of patient sex on immune therapy outcomes.

Redirecting antibody responses from egg-adapted epitopes following repeat vaccination with recombinant or cell culture-based versus egg-based influenza vaccines

Repeat vaccination with egg-based influenza vaccines could preferentially boost antibodies targeting the egg-adapted epitopes and reduce immunogenicity to circulating viruses. In this randomized trial (Clinicaltrials.gov: NCT03722589), sera pre- and post-vaccination with quadrivalent inactivated egg-based (IIV4), cell culture-based (ccIIV4), and recombinant (RIV4) influenza vaccines were collected from healthcare personnel (18-64 years) in 2018−19 (N = 723) and 2019−20 (N = 684) influenza seasons. We performed an exploratory analysis. Vaccine egg-adapted changes had the most impact on A(H3N2) immunogenicity. In year 1, RIV4 induced higher neutralizing and total HA head binding antibodies to cell- A(H3N2) virus than ccIIV4 and IIV4. In year 2, among the 7 repeat vaccination arms (IIV4-IIV4, IIV4-ccIIV4, IIV4-RIV4, RIV4-ccIIV4, RIV4-RIV4, ccIIV4-ccIIV4 and ccIIV4-RIV4), repeat vaccination with either RIV4 or ccIIV4 further improved antibody responses to circulating viruses with decreased neutralizing antibody egg/cell ratio. RIV4 also had higher post-vaccination A(H1N1)pdm09 and A(H3N2) HA stalk antibodies in year 1, but there was no significant difference in HA stalk antibody fold rise among vaccine groups in either year 1 or year 2. Multiple seasons of non-egg-based vaccination may be needed to redirect antibody responses from immune memory to egg-adapted epitopes and re-focus the immune responses towards epitopes on the circulating viruses to improve vaccine effectiveness.

Safety, tolerability, and immunogenicity of PIKA-adjuvanted recombinant SARS-CoV-2 spike protein subunit vaccine in healthy adults: an open-label randomized phase I clinical trial.

This phase I study aimed to assess the safety, tolerability, and immunogenicity of the PIKA-adjuvanted recombinant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein subunit vaccine in healthy adults aged 18 years and older. This is a phase I, open-label, dose-escalation study at three dose levels (5 µg, 10 µg, and 20 µg) of the PIKA coronavirus disease 2019 (COVID-19) vaccine administered intramuscularly. The three vaccine arms are (A) subjects who have never received any COVID-19 vaccination or have had COVID-19 infection for >6 months prior to enrolment; (B1) subjects whose COVID-19 primary vaccination series was completed with an inactivated COVID-19 vaccine; and (B2) subjects whose primary series was completed with messenger RNA COVID-19 vaccine. Subjects who reported solicited adverse events (AEs) within seven days post-vaccination ranged from 35% to 60% within each vaccine arm. Most solicited AEs were mild local pain and tenderness. Systemic solicited AEs were only reported in Arm A. In all three vaccine arms, neutralizing antibody geometric mean titers were highest at day 28 (Arms B1 and B2) or day 35 (Arm A) than at baseline for all dose levels against the Wuhan (wild original SARS-CoV-2 virus, Wuhan-Hu-1), Delta (B.1.617.2), and Omicron (B.1.1.529) variants. These were sustained at day 183. Seroconversion rates at day 35 (Arm A, 85.7%-92.9%) or day 183 (Arms B1, 90.9%-100.0%, and B2, 18.2%-36.4%) and geometric mean fold rises were highest in the 5-µg dose level against all three variants. The PIKA-adjuvanted recombinant SARS-CoV-2 S protein subunit vaccine showed promising immunogenicity profile with no safety concerns. A dose-dependent immune response was observed, with slight advantages seen in low-dose (5 µg and 10 µg) groups (ClinicalTrials.gov registration number: NCT05305300).

Immunogenicity and safety of HavisureTM vaccine developed by Human Biologicals Institute in healthy subjects of 12 months to 49 years of age: A phase II/III, randomized, single blind, non-inferiority study

BackgroundHepatitis A is an inflammation of the liver caused by the hepatitis A virus (HAV). It is transmitted mainly because of poor personal hygiene via the faecal/oral route through ingestion of contaminated food or water or through the direct contact with an infectious person. Though most of the infected individuals recover from the infection, a few may develop fatal fulminant hepatitis. In this randomized, multicenter study, immunogenicity and safety of Havisure™ vaccine of Human Biologicals Institute was compared with Havrix® vaccine. MethodsThe study was carried out in 528 eligible healthy subjects, in two age groups across eight centres in India. Group A included subjects of 19–49 years and Group B subjects of 12 months to below 19 years of age. All subjects received two doses of either Havisure™ vaccine or Havrix® vaccine as per randomization at six months interval. Blood samples for antibody titre estimation were collected before vaccination and 4–6 weeks after 2nd dose of vaccination. Immunogenicity was assessed by estimating seroconversion rate, seroprotection rate, and geometric mean titres of antibodies. Safety was evaluated by collection and analysis of data on solicited and unsolicited adverse events. ResultsOf 528 enrolled subjects, 493 subjects completed the study. There was 100% seroconversion and seroprotection in both the vaccine arms. There was no statistical difference in the geometric mean titres between the two vaccine arms. Pain and swelling at the site of injection were the most common local adverse events whereas fever and headache were the most common systemic adverse events observed in both vaccine arms. No serious adverse event was reported in the study. ConclusionThe study results indicate that the Havisure™ vaccine is immunogenic and safe when administered to healthy subjects of 12 months to 49 years of age, and is non-inferior to Havrix® Vaccine.

Immunogenicity and safety of Mebella™ vaccine developed by Human Biologicals Institute in a Phase II/III, randomized, multicentric, non-inferiority study

BackgroundThe goal of ‘Measles and Rubella Strategic Framework 2021-2030’ is to make “A world free from measles and rubella”. To be a part of this journey, Human Biologicals Institute has developed Mebella™ vaccine, which is a lyophilized Measles and Rubella (Live) vaccine. A randomized, single blind, comparative, multicenter Phase II/III trial was conducted to compare the immunogenicity and safety of Mebella™ vaccine with MR-VAC® vaccine in healthy subjects. MethodsA total of 888 subjects were enrolled in four age groups (222 subjects in each group) of 18 years to 49 years; 2 years to below 18 years; 12 months to below 24 months; and 9 months to below 12 months of age. The subjects were randomized in 2:1 ratio to receive single dose of either Mebella™ vaccine of Human Biologicals Institute or MR-VAC® vaccine. Immunogenicity was assessed at 42 days after the vaccination and was compared between the vaccine arms in each group. Safety was also assessed and compared between the vaccine arms during the study period. ResultsA total of 875 subjects completed the study out of 888 enrolled subjects. The seroprotection rates, seroconversion rates, and geometric mean titres for both Measles and Rubella components of Mebella™ vaccine were found to be comparable and non-inferior to the MR-VAC® vaccine after 42 days of vaccination. Injection site pain was the most common local adverse event reported whereas fever was the only systemic adverse event reported in both the vaccine arms. No serious adverse event was reported. ConclusionIt was concluded from the study results that the test vaccine, Mebella™, was immunogenic and well tolerated and was non-inferior to the comparator vaccine, MR-VAC®, when administered to healthy subjects of 9 months to 49 years of age.Clinical Trial Registry of India Identifier: CTRI/2020/07/026930.

Mechanistic Model Describing the Time Course of Humoral Immunity Following Ad26.COV2.S Vaccination in Non-Human Primates.

Mechanistic modeling can be used to describe the time course of vaccine-induced humoral immunity and to identify key biologic drivers in antibody production. We used a six-compartment mechanistic model to describe a 20-week time course of humoral immune responses in 56 non-human primates (NHPs) elicited by vaccination with Ad26.COV2.S according to either a single-dose regimen (1 × 1011 or 5 × 1010 viral particles [vp]) or a two-dose homologous regimen (5 × 1010 vp) given in an interval of 4 or 8 weeks. Humoral immune responses were quantified by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike-specific binding antibody concentrations as determined by spike protein-enzyme-linked immunosorbent assay. The mechanistic model adequately described the central tendency and variability of binding antibody concentrations through 20 weeks in all vaccination arms. The estimation of mechanistic modeling parameters revealed greater contribution of the antibody production mediated by short-lived cells as compared with long-lived cells in driving the peak response, especially post second dose when a more rapid peak response was observed. The antibody production mediated by long-lived cells was identified as relevant for generating the first peak and for contributing to the long-term time course of sustained antibody concentrations in all vaccination arms. The findings contribute evidence on the key biologic components responsible for the observed time course of vaccine-induced humoral immunity in NHPs and constitute a step toward defining immune biomarkers of protection against SARS-CoV-2 that might translate across species. SIGNIFICANCE STATEMENT: We demonstrate the adequacy of a mechanistic modeling approach describing the time course of binding antibody concentrations in non-human primates (NHPs) elicited by different dose levels and regimens of Ad26.COV2.S. The findings are relevant for informing the mechanism-based accounts of vaccine-induced humoral immunity in NHPs and translational research efforts aimed at identifying immune biomarkers of protection against SARS-CoV-2 infection.

Long-Term Results of Immunogenicity of Booster Vaccination against SARS-CoV-2 (Hybrid COV-RAPEL TR Study) in Turkiye: A Double-Blind, Randomized, Controlled, Multicenter Phase 2 Clinical Study.

The immunogenicity of vaccines decreases over time, causing a need for booster doses. This study aimed to present the long-term (Day 84) immunogenicity results of the double-blind, randomized, controlled, phase II Hybrid COV-RAPEL TR Study (NCT04979949), in which the TURKOVAC or CoronaVac vaccines were used as a booster after the second dose of primary vaccination with CoronaVac. A total of 190 participants from the Hybrid COV-RAPEL TR Study, who had both Day 28 and Day 84 immunogenicity results, were included. The immunogenicity on Day 84, regarding the neutralizing antibody positivity (Wuhan and Delta variants) and anti-spike immunoglobulin (Ig) G (IgG) antibody positivity, was compared between TURKOVAC and CoronaVac vaccine arms according to sex and age groups. Overall, antibody positivity showed a slight decrease on Day 84 vs. Day 28, but was not different between TURKOVAC and CoronaVac arms either for sexes or for age groups. However, TURKOVAC produced better antibody response against the Delta variant than CoronaVac, while CoronaVac was superior over TURKOVAC regarding neutralizing antibody positivity in the 50-60 years age group, regardless of the variant. A single booster dose, after the completion of the primary vaccination, increases antibody positivity on Day 28 which persists until Day 84 with a slight decrease. However, an additional booster dose may be required thereafter, since the decrease in antibody titer may be faster over time.

Modifiers of COVID-19 vaccine efficacy: Results from four COVID-19 prevention network efficacy trials

Questions remain regarding the effect of baseline host and exposure factors on vaccine efficacy (VE) across pathogens and vaccine platforms. We report placebo-controlled data from four Phase 3 COVID-19 trials during the early period of the pandemic. This was a cross-protocol analysis of four randomized, placebo-controlled efficacy trials (Moderna/mRNA1273, AstraZeneca/AZD1222, Janssen/Ad26.COV2.S, and Novavax/NVX-CoV2373) using a harmonized design. Trials were conducted in the United States and international sites in adults ≥ 18 years of age. VE was assessed for symptomatic and severe COVID-19. We analyzed 114,480 participants from both placebo and vaccine arms, enrolled July 2020 to February 2021, with follow up through July 2021. VE against symptomatic COVID-19 showed little heterogeneity across baseline socio-demographic, clinical or exposure characteristics, in either univariate or multivariate analysis, regardless of vaccine platform. Similarly, VE against severe COVID-19 in the single trial (Janssen) with sufficient endpoints for analysis showed little evidence of heterogeneity. COVID-19 VE is not influenced by baseline host or exposure characteristics across efficacy trials of different vaccine platforms and countries when well matched to circulating virus strains. This supports use of these vaccines, regardless of platform type, as effective tools in the near term for reducing symptomatic and severe COVID-19, particularly for older individuals and those with common co-morbidities during major variant shifts. Clinical trial registration numbers: NCT04470427, NCT04516746, NCT04505722, and NCT04611802.

Assessing the feasibility of Phase 3 vaccine trials against Marburg Virus Disease: A modelling study

BackgroundOutbreaks of Marburg virus disease (MVD) are rare and small in size, with only 18 recorded outbreaks since 1967, only two of which involved more than 100 cases. It has been proposed, therefore, that Phase 3 trials for MVD vaccines should be held open over multiple outbreaks until sufficient end points accrue to enable vaccine efficacy (VE) to be calculated. Here we estimate how many outbreaks might be needed for VE to be estimated. MethodsWe adapt a mathematical model of MVD transmission to simulate a Phase 3 individually randomised placebo controlled vaccine trial. We assume in the base case that vaccine efficacy is 70% and that 50% of individuals in affected areas are enrolled into the trial (1:1 randomisation). We further assume that the vaccine trial starts two weeks after public health interventions are put in place and that cases occurring within 10 days of vaccination are not included in VE calculations. ResultsThe median size of simulated outbreaks was 2 cases. Only 0.3% of simulated outbreaks were predicted to have more than 100 MVD cases. 95% of simulated outbreaks terminated before cases accrued in the placebo and vaccine arms. Therefore the number of outbreaks required to estimate VE was large: after 100 outbreaks, the estimated VE was 69% but with considerable uncertainty (95% CIs: 0%−100%) while the estimated VE after 200 outbreaks was 67% (95% CIs: 42%−85%). Altering base-case assumptions made little difference to the findings. In a sensitivity analysis, increasing R0 by 25% and 50% led to an estimated VE after 200 outbreaks of 69% (95% CIs: 53–85%) and 70% (95% CIs: 59–82%), respectively. ConclusionsIt is unlikely that the efficacy of any candidate vaccine can be calculated before more MVD outbreaks have occurred than have been recorded to date. This is because MVD outbreaks tend to be small, public health interventions have been historically effective at reducing transmission, and vaccine trials are only likely to start after these interventions are already in place. Hence, it is expected that outbreaks will terminate before, or shortly after, cases start to accrue in the vaccine and placebo arms.

Immunogenicity and clinical activity of tipapkinogen sovacivec (TG4001), an HPV-16 cancer vaccine: A randomized phase 2 study in advanced anogenital cancers.

2630 Background: Human papillomavirus 16 (HPV-16) infection is associated with several cancer types with limited treatment options in the locally R/M settings. Furthermore, immune checkpoint inhibitors have limited activity against advanced HPV-cancers. TG4001 is a viral vector vaccine targeting HPV E6 and E7 antigens. We have previously shown in a single-arm, dose finding phase 1 study that TG4001 combined with PD-L1 blockade using avelumab was safe and associated with a response rate of 22%. Herein we report preliminary data on immunogenicity and clinical activity of TG4001 in a randomized phase 2 study comparing TG4001 plus avelumab versus avelumab alone. Methods: Eligibility criteria: R/M HPV16+ anogenital cancer including cervical, vulvar, vaginal, penile, and anal cancers; immunotherapy naïve and with no more than one prior line of chemotherapy. HPV-16 positivity was required and centrally determined using a PCR based assay. Patients were randomly assigned 1:1 to receive either TG4001 plus avelumab (Vaccine arm) or avelumab alone. Randomization was stratified by tumor type (cervical, anal, genital). TG4001 was administered s.c at 5·107 pfu, Q1w for 5 weeks, then Q2w until month 6 followed by Q12w until progressive disease and avelumab i.v at 800 mg Q2w until progressive disease. PBMCwere collected at baseline, day 43 and day 85 to assess T-cell responses against E6 and E7 antigens using ex-vivo IFNg ELISPOT and immunophenotyping of circulating T cells. Vaccine immune response (IR) was defined as onset of a new T-cell response against either antigen or amplification of a pre-existing response under treatment. Tumor response was assessed using RECIST 1.1. Results: 59 pts had been randomized by the time of data cut-off. IR was assessed in 24 pts in the vaccine arm and 16 pts in the avelumab arm. T cells against E6 or E7 antigens at baseline were rare with only 4 pts having a low intensity ELISPOT readout against either target prior to initiation of treatment. 11/24 pts in the vaccine arm had an IR, while none of the patients in the avelumab arm had an IR. Occurrence of IR was detected at day 43 and tended to gain in intensity at D85. In the vaccine arm, IR was associated with tumor response with 3 clinical responders among 11 pts with positive IR versus 1 response observed among the 13 patients without IR. Conversely, only 2 progressive disease pts among 11 positive IR compared favorably to the 6/13 vaccine arm pts with no IR. Remarkably, a complete clinical response was observed in a vaccine treated pt exhibiting the strongest E6 and E7 IR. Conclusions: TG4001 can induce a de novo immune response against HPV-16 antigens E6 and E7 in advanced HPV-16 cancers. The data suggest that these IRs are associated with anti-tumor response and that TG4001 vaccination in combination with ICI has the potential to drive clinical benefit in R/M anogenital cancers. Clinical trial information: NCT03260023 .

Clinical outcomes in patients with metastatic non-small cell lung cancer and head and neck squamous cell cancer treated with immune checkpoint inhibitors according to COVID-19 vaccination status.

e14696 Background: Immune checkpoint inhibitor (ICI) constitute the mainstay of therapy in metastatic non-small cell lung cancer (NSCLC) and head and neck squamous cell cancer (HNSCC). Infectious vaccines administered intratumorally or systemically have been suggested to enhance response to ICI and improve outcomes. No data is available on the effect of COVID-19 vaccines on clinical outcomes in patients treated with ICI. The aim of the study is to investigate overall survival (OS), progression-free survival (PFS), and immune related adverse events (IRAEs) according to mRNA COVID-19 vaccination status in patients with metastatic NSCLC and HNSCC who were treated with ICI. Methods: We performed retrospective analysis of clinical outcomes between a cohort of patients treated with ICI who received at least one dose of COVID-19 vaccine, and a historic control group of patients who did not receive COVID-19 vaccine and did not have documented COVID-19 infection. We included patients with metastatic NSCLC and HNSCC who had received at least one dose of ICI, either as monotherapy or in combination with chemotherapy or targeted therapy. Patients were stratified by age, gender, ethnicity, COVID-19 vaccination status, number of vaccinations, treatment type (monotherapy versus combined), treatment line, and PD-L1 status. Endpoints included IRAEs, PFS and OS. Results: A total of 151 patients met inclusion criteria (94 vaccinated and 57 control). Mean age at diagnosis was 62 years, the majority were female (51%), African American (58.3%), and received ICI monotherapy (57.6%). There was prolonged OS in patients who received COVID-19 vaccination versus control group ( p-value=0.04). In a multivariate analysis, patients in the COVID-19 vaccine arm had significantly reduced hazard of dying (HR:0.49, p =0.0446) when controlled for all of the above variables, and each additional received vaccine was associated with significant reduced hazard (HR=0.701, p-value = 0.0099). Race and type of cancer were statistically associated with PFS. Controlled for these factors, COVID arm patients had reduced hazard of disease progression (HR = 0.58, p-value = 0.0506), and each additional received mRNA vaccine was associated with a significantly reduced hazard of progression (HR = 0.74, p-value = 0.0046). There was no significant difference in the rate of IRAEs between vaccinated and non-vaccinated patients ( p=0.71). Conclusions: In this sample of patients with metastatic NSCLC and HNSCC who received ICI, there was significant improvement in OS between patients who received a COVID-19 vaccine compared patients who did not receive vaccination and did not have COVID-19 infection. There were no significant differences in IRAEs. Further studies are required to assess whether there is a synergistic effect between COVID-19 vaccination and ICI efficacy.

Persistence of immune responses after heterologous and homologous third COVID-19 vaccine dose schedules in the UK: eight-month analyses of the COV-BOOST trial

COV-BOOST is a multicentre, randomised, controlled, phase 2 trial of seven COVID-19 vaccines used as a third booster dose in June 2021. Monovalent messenger RNA (mRNA) COVID-19 vaccines were subsequently widely used for the third and fourth-dose vaccination campaigns in high-income countries. Real-world vaccine effectiveness against symptomatic infections following third doses declined during the Omicron wave. This report compares the immunogenicity and kinetics of responses to third doses of vaccines from day (D) 28 to D242 following third doses in seven study arms. The trial initially included ten experimental vaccine arms (seven full-dose, three half-dose) delivered at three groups of six sites. Participants in each site group were randomised to three or four experimental vaccines, or MenACWY control. The trial was stratified such that half of participants had previously received two primary doses of ChAdOx1 nCov-19 (Oxford-AstraZeneca; hereafter referred to as ChAd) and half had received two doses of BNT162b2 (Pfizer-BioNtech, hereafter referred to as BNT). The D242 follow-up was done in seven arms (five full-dose, two half-dose). The BNT vaccine was used as the reference as it was the most commonly deployed third-dose vaccine in clinical practice in high-income countries. The primary analysis was conducted using all randomised and baseline seronegative participants who were SARS-CoV-2 naïve during the study and who had not received a further COVID-19 vaccine for any reason since third dose randomisation. Among the 817 participants included in this report, the median age was 72 years (IQR: 55-78) with 50.7% being female. The decay rates of anti-spike IgG between vaccines are different among both populations who received initial doses of ChAd/ChAd and BNT/BNT. In the population that previously received ChAd/ChAd, mRNA vaccines had the highest titre at D242 following their vaccine dose although Ad26. COV2. S (Janssen; hereafter referred to as Ad26) showed slower decay. For people who received BNT/BNT as their initial doses, a slower decay was also seen in the Ad26 and ChAd arms. The anti-spike IgG became significantly higher in the Ad26 arm compared to the BNT arm as early as 3 months following vaccination. Similar decay rates were seen between BNT and half-BNT; the geometric mean ratios ranged from 0.76 to 0.94 at different time points. The difference in decay rates between vaccines was similar for wild-type live virus-neutralising antibodies and that seen for anti-spike IgG. For cellular responses, the persistence was similar between study arms. Heterologous third doses with viral vector vaccines following two doses of mRNA achieve more durable humoral responses compared with three doses of mRNA vaccines. Lower doses of mRNA vaccines could be considered for future booster campaigns.