Interim analysis from a phase 2 randomized trial of EuCorVac-19: a recombinant protein SARS-CoV-2 RBD nanoliposome vaccine.

BACKGROUND: Numerous vaccine strategies are being advanced to control SARS-CoV-2, the cause of the COVID-19 pandemic. EuCorVac-19 (ECV19) is a recombinant protein nanoparticle vaccine that displays the SARS-CoV-2 receptor-binding domain (RBD) on immunogenic nanoliposomes. METHODS: Initial study of a phase 2 randomized, observer-blind, placebo-controlled trial to assess the immunogenicity, safety, and tolerance of ECV19 was carried out between July and October 2021. Two hundred twenty-nine participants were enrolled at 5 hospital sites in South Korea. Healthy adults aged 19-75 without prior known exposure to COVID-19 were vaccinated intramuscularly on day 0 and day 21. Of the participants who received two vaccine doses according to protocol, 100 received high-dose ECV19 (20 µg RBD), 96 received low-dose ECV19 (10 µg RBD), and 27 received placebo. Local and systemic adverse events were monitored. Serum was assessed on days 0, 21, and 42 for immunogenicity analysis by ELISA and neutralizing antibody response by focus reduction neutralization test (FRNT). RESULTS: Low-grade injection site tenderness and pain were observed in most participants. Solicited systemic adverse events were less frequent, and mostly involved low-grade fatigue/malaise, myalgia, and headache. No clinical laboratory abnormalities were observed. Adverse events did not increase with the second injection and no serious adverse events were solicited by ECV19. On day 42, Spike IgG geometric mean ELISA titers were 0.8, 211, and 590 Spike binding antibody units (BAU/mL) for placebo, low-dose and high-dose ECV19, respectively (p < 0.001 between groups). Neutralizing antibodies levels of the low-dose and high-dose ECV19 groups had FRNT50 geometric mean values of 129 and 316, respectively. Boosting responses and dose responses were observed. Antibodies against the RBD correlated with antibodies against the Spike and with virus neutralization. CONCLUSIONS: ECV19 was generally well-tolerated and induced antibodies in a dose-dependent manner that neutralized SARS-CoV-2. The unique liposome display approach of ECV19, which lacks any immunogenic protein components besides the antigen itself, coupled with the lack of increased adverse events during boosting suggest the vaccine platform may be amenable to multiple boosting regimes in the future. Taken together, these findings motivate further investigation of ECV19 in larger scale clinical testing that is underway. TRIAL REGISTRATION: The trial was registered at ClinicalTrials.gov as # NCT04783311.

Development of a new 15-valent pneumococcal conjugate vaccine (PCV15) and evaluation of its immunogenicity.

A new 15-valent pneumococcal conjugate vaccine (PCV15) against serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 11A, 14, 18C, 19A, 19F, 22F, and 23F has been developed using aluminum phosphate as an adjuvant. Using the rabbit model, immunogenicity of each serotype was evaluated by measuring antigen specific antibodies and functional antibody titers and comparing them to a control vaccine, Prevnar13®. Among the shared serotypes in both PCV15 and Prevnar13®, Type 3 and 23F in PCV15 exhibited a lower opsonic index than Prevnar13®. Conversely, the other types showed greater or nearly the same immunogenic effects. Type 11A and 22F are two additional serotypes included in PCV15, and only 22F showed a reasonable opsonic index compared with other types. Type 11A exhibited a basal level fold-increase in OPA; thus, we further optimized 11A as well as 3 and 23F by controlling the polysaccharide-to-protein conjugation ratio as a variable. Antibody levels and functional antibody activities were evaluated by ELISA and OPA, and improved levels of immunogenic activities were observed for all three serotypes. In this study, we propose a new PCV15 candidate, in which the common 13 serotypes and a licensed control vaccine have equivalent efficacy while two additional serotypes showed adequate immunogenicity in the rabbit model.

One-year antibody durability induced by EuCorVac-19, a liposome-displayed COVID-19 receptor binding domain subunit vaccine, in healthy Korean subjects.

OBJECTIVE: EuCorVac-19 (ECV-19), an adjuvanted liposome-displayed receptor binding domain (RBD) COVID-19 vaccine, previously reported interim Phase 2 trial results showing induction of neutralizing antibodies 3 weeks after prime-boost immunization. The objective of this study was to determine the longer-term antibody response of the vaccine. METHODS: To assess immunogenicity 6 and 12 months after vaccination, participants in the Phase 2 trial (NCT04783311) were excluded if they: 1) withdrew, 2) reported COVID-19 infection or additional vaccination, or 3) exhibited increasing Spike (S) antibodies (representing possible non-reported infection). Following exclusions, of the 197 initial subjects, anti-S IgG antibodies and neutralizing antibodies were further assessed in 124 subjects at the 6-month timepoint, and 36 subjects at the 12-month timepoint. RESULTS: Median anti-S antibody half-life was 52 days (interquartile range [IQR]:42-70), in the "early" period from 3 weeks to 6 months, and 130 days (IQR:97-169) in the "late" period from 6 to 12 months. There was a negative correlation between initial antibody titer and half-life. Anti-S and neutralizing antibody responses were correlated. Neutralizing antibody responses showed longer half-lives; the early period had a median half-life of 120 days (IQR:81-207), and the late period had a median half-life of 214 days (IQR:140-550). CONCLUSION: These data establish antibody durability of ECV-19, using a framework to analyze COVID-19 vaccine-induced antibodies during periods of high infection.

Safety and immunogenicity of the Euvichol-S oral cholera vaccine for prevention of Vibrio cholerae O1 infection in Nepal: an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial.

BACKGROUND: In October, 2017, WHO launched a strategy to eliminate cholera by 2030. A primary challenge in meeting this goal is the limited global supply capacity of oral cholera vaccine and the worsening of cholera outbreaks since 2021. To help address the current shortage of oral cholera vaccine, a WHO prequalified oral cholera vaccine, Euvichol-Plus was reformulated by reducing the number of components and inactivation methods. We aimed to evaluate the immunogenicity and safety of Euvichol-S (EuBiologics, Seoul, South Korea) compared with an active control vaccine, Shanchol (Sanofi Healthcare India, Telangana, India) in participants of various ages in Nepal. METHODS: We did an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial at four hospitals in Nepal. Eligible participants were healthy individuals aged 1-40 years without a history of cholera vaccination. Individuals with a history of hypersensitivity reactions to other preventive vaccines, severe chronic disease, previous cholera vaccination, receipt of blood or blood-derived products in the past 3 months or other vaccine within 4 weeks before enrolment, and pregnant or lactating women were excluded. Participants were randomly assigned (1:1:1:1) by block randomisation (block sizes of two, four, six, or eight) to one of four groups (groups A-D); groups C and D were stratified by age (1-5, 6-17, and 18-40 years). Participants in groups A-C were assigned to receive two 1·5 mL doses of Euvichol-S (three different lots) and participants in group D were assigned to receive the active control vaccine, Shanchol. All participants and site staff (with the exception of those who prepared and administered the study vaccines) were masked to group assignment. The primary immunogenicity endpoint was non-inferiority of immunogenicity of Euvichol-S (group C) versus Shanchol (group D) at 2 weeks after the second vaccine dose, measured by the seroconversion rate, defined as the proportion of participants who had achieved seroconversion (defined as ≥four-fold increase in V cholerae O1 Inaba and Ogawa titres compared with baseline). The primary immunogenicity endpoint was assessed in the per-protocol analysis set, which included all participants who received all their planned vaccine administrations, had no important protocol deviations, and who provided blood samples for all immunogenicity assessments. The primary safety endpoint was the number of solicited adverse events, unsolicited adverse events, and serious adverse events after each vaccine dose in all ages and each age stratum, assessed in all participants who received at least one dose of the Euvichol-S or Shanchol. Non-inferiority of Euvichol-S compared with Shanchol was shown if the lower limit of the 95% CI for the difference between the seroconversion rates in Euvichol-S group C versus Shanchol group D was above the predefined non-inferiority margin of -10%. The trial was registered at ClinicalTrials.gov, NCT04760236. FINDINGS: Between Oct 6, 2021, and Jan 19, 2022, 2529 healthy participants (1261 [49·9%] males; 1268 [50·1%] females), were randomly assigned to group A (n=330; Euvichol-S lot number ES-2002), group B (n=331; Euvichol-S ES-2003), group C (n=934; Euvichol-S ES-2004]), or group D (n=934; Shanchol). Non-inferiority of Euvichol-S versus Shanchol in seroconversion rate for both serotypes at 2 weeks after the second dose was confirmed in all ages (difference in seroconversion rate for V cholerae O1 Inaba -0·00 [95% CI -1·86 to 1·86]; for V cholerae O1 Ogawa -1·62 [-4·80 to 1·56]). Treatment-emergent adverse events were reported in 244 (9·7%) of 2529 participants in the safety analysis set, with a total of 403 events; 247 events were reported among 151 (9·5%) of 1595 Euvichol-S recipients and 156 events among 93 (10·0%) of 934 Shanchol recipients. Pyrexia was the most common adverse event in both groups (57 events among 56 [3·5%] of 1595 Euvichol-S recipients and 37 events among 35 [3·7%] of 934 Shanchol recipients). No serious adverse events were deemed to be vaccine-related. INTERPRETATION: A two-dose regimen of Euvichol-S vaccine was non-inferior to the active control vaccine, Shanchol, in terms of seroconversion rates 2 weeks after the second dose. The simplified formulation and production requirements of the Euvichol-S vaccine have the potential to increase the supply of oral cholera vaccine and reduce the gap between the current oral cholera vaccine supply and demand. FUNDING: The Bill & Melinda Gates Foundation. TRANSLATION: For the Nepali translation of the abstract see Supplementary Materials section.

Comparison of the immunogenicity and safety of Euvichol-Plus with Shanchol in healthy Indian adults and children: an open-label, randomised, multicentre, non-inferiority, parallel-group, phase 3 trial.

Background: Considering the cholera menace in India and to seek licensure of the oral cholera vaccine (OCV), Euvichol-Plus, we conducted a clinical trial to compare the immunogenicity and safety of Euvichol-Plus with Shanchol in healthy Indian adults and children. Methods: This phase 3, open-label, multicentre, randomised, non-inferiority, parallel-group, comparative study was conducted at seven sites across India involving 416 healthy adults (aged ≥18-60 years) and children (aged ≥1 to <18 years). Healthy individuals who agreed to participate through a voluntary written informed consent form along with oral or written assent (for children aged 7-18 years) were included. No assent was required for those <7 years, as consent was given by the legally acceptable representatives (LAR). Participants were randomised 1:1 to receive two doses of either Euvichol-Plus or Shanchol orally, 14 days apart. The first dose (1.5 ml) was administered on visit 1, and the second dose at 2 weeks after the first dose during visit 2. Participants were followed up telephonically for 3 consecutive days after each visit and returned for final assessment at 2 weeks after the second dose (visit 3). Blood samples were collected for immunogenicity assessment, and safety analyses were done during all the visits. The primary immunogenicity endpoint was the percentage of participants with ≥4-fold increase in anti-Vibrio cholerae (V. cholerae) O1 Ogawa and O1 Inaba (vibriocidal) antibody titres at 2 weeks after the second dose as compared to baseline titres prior to dosing. The secondary immunogenicity endpoints included the percentage of participants with ≥4-fold increase in anti-V. cholerae O139 antibody titres at 2 weeks after the second dose as compared to baseline titres, and geometric mean titres (GMT) and geometric mean ratios (GMR) as measured by anti-V. cholerae O1 Ogawa, O1 Inaba, and O139 antibody titres at 2 weeks after the second dose as compared to baseline titres. The safety endpoints included assessment of solicited, unsolicited adverse events (AEs), and serious adverse events (SAEs). The clinical trial was registered with the Clinical Trials Registry of India (CTRI/2021/08/035344). Findings: The study was performed in two age cohorts: cohort 1 (aged ≥18-60 years, 208 participants [104 in Euvichol-Plus group and 104 in Shanchol group]), and cohort 2 (aged ≥1 to <18 years, 208 participants [104 in Euvichol-Plus group and 104 in Shanchol group]). A total of 414 participants (Euvichol-Plus: 206 and Shanchol: 208) who completed the study (intention-to-treat and per-protocol set) were analysed to compare the vibriocidal titre as an index for immunogenicity. At 2 weeks after the second dose, the percentage of participants in the Euvichol-Plus group who reported a ≥4-fold increase in anti-V. cholerae antibody titres were 68.93% (O1 Ogawa) [95% CI 62.13%-75.18%], 66.02% (O1 Inaba) [95% CI 59.11%-72.46%], and 59.71% (O139) [95% CI 52.67%-66.47%] as compared to 63.94% (O1 Ogawa) [95% CI 57.01%-70.47%], 65.87% (O1 Inaba) [95% CI 58.99%-72.28%], and 56.25% (O139) [95% CI 49.22%-63.10%] in the Shanchol group. The lower limit of 95% CI for treatment difference for all the antibody titres was ≥10% (non-inferiority margin), demonstrating that Euvichol-Plus was non-inferior to Shanchol. The post-vaccination GMT (Day 14 and 28) were more than the pre-vaccination GMT for all three serotypes in both groups. The GMR obtained for Euvichol-Plus over Shanchol for O1 Ogawa, O1 Inaba, and O139 serotypes was >1, indicating non-inferiority of Euvichol-Plus to Shanchol. The safety cohort included 416 participants. Headache was the most common solicited AE, whereas cold and cough were the most common unsolicited AEs in both groups. Interpretation: Euvichol-Plus appears to be non-inferior to Shanchol in terms of immunogenicity and safety in healthy Indian adults and children. Funding: Techinvention Lifecare Private Limited, Mumbai, India.

An open-label, comparative, single dose, clinical Phase â study to assess the safety and immunogenicity of typhoid conjugate vaccine (Vi-CRM197) in healthy Filipino adults.

An injectable typhoid conjugate vaccine (TCV) provides longer-lasting protection, requires fewer doses, and is suitable for children aged >2 years. In addition, TCV is preferred at most ages owing to its improved immunological properties as it overcomes the limitation of Vi polysaccharide vaccines. Here, we assessed the safety, tolerability, and immunogenicity of a TCV, Vi-CRM197, termed EuTCV, in an open-label clinical phase I study in healthy Filipino adults. This study was conducted in 75 healthy adults aged 18-45 years who were randomized in a 1:1:1 ratio based on the vaccines administered: EuTCV (Test), Typbar-TCV® (WHO prequalified vaccine) and Typhim Vi® (Vi polysaccharide vaccine). The study vaccines were administered at a dose of 25 µg of Vi-CRM197 conjugate by intramuscular injection as a single dose to each of the 25 participants/group, and their immunogenicity and overall safety were assessed for 42 days post-vaccination. All study participants (n = 25/group) completed the trial without dropouts. There were no deaths, SAEs, or events leading to premature withdrawal from the study. Anti-Vi IgG antibody titer (geometric mean titer) of EuTCV group on day 42 was 65.325 [95% CI (36.860, 115.771)], which was significantly higher than that of the WHO prequalified TCV [24.795, 95% CI (16.164, 38.033) p = 0.0055] and the Vi polysaccharide vaccine [7.998, 95% CI (3.800, 16.835) p < 0.0001]. Moreover, the seroconversion rate of EuTCV and Typbar-TCV® was 100%, but that of Typhim Vi® was only 84%. The IgG1-3 subclass titers and serum bactericidal assay results in the EuTCV group showed higher and better bactericidal capacity than the other groups. EuTCV was well tolerated and exhibited an acceptable safety profile in the study population. The Vi-CRM197 conjugate dose of 25 µg may be considered effective in terms of efficacy and safety. ClinicalTrials.gov registration number: NCT03956524.

Reduction of free polysaccharide contamination in the production of a 15-valent pneumococcal conjugate vaccine.

Glycoconjugate vaccines are vaccines in which a bacterial polysaccharide antigen is conjugated to a carrier protein to enhance immunogenicity by promoting T cell-dependent immune response. However, the free (unreacted) polysaccharides remaining after the conjugation process can inhibit the immunogenicity of a conjugate vaccine. Thus, we aimed to reduce the unbound free polysaccharides in the polysaccharide-protein conjugation process for the development of a new 15-valent pneumococcal conjugate vaccine (PCV15) by varying some factors that may affect the conjugation results such as polysaccharide/protein ratio, polysaccharide size, and concentration of a coupling agent in a conjugation reaction mixture. Concentrations of a coupling agent, carbodiimide (EDAC), and a carrier protein (CRM197) used in PCV15 production, during the conjugation process, had little effect on the content of free polysaccharides. However, the size of the polysaccharide was identified as the critical factor to control the free polysaccharide content, with an inverse relationship observed between the molecular weight of the polysaccharide and the residual free polysaccharide content after conjugation. Based on these results, a new PCV15 with low free polysaccharide contamination was produced and tested for immunogenicity using a rabbit model to show that it induces similar level of immune responses in rabbits compared to a comparator vaccine Prevnar13®.

Quality Improvement of Capsular Polysaccharide in Streptococcus pneumoniae by Purification Process Optimization.

Streptococcus pneumoniae is the causative agent of many diseases, most notably pneumonia. Most of the currently used vaccines to protect against this pathogen employ pneumococcal capsular polysaccharides (CPSs) as antigens, but purifying CPS of sufficient quality has been challenging. A purification process for CPS comprising conventional methods such as ultrafiltration, CTAB precipitation, and chromatography was previously established; however, this method resulted in high cell wall polysaccharide (CWPS) contamination, especially for serotype 5. Thus, a better purification method that yields CPS of a higher quality is needed for vaccine development. In this study, we significantly reduced CWPS contamination in serotype 5 CPS by improving the ultrafiltration and CTAB precipitation steps. Moreover, by applying an acid precipitation process to further remove other impurities, serotype 5 CPS was obtained with a lower impurity such as decreased nucleic acid contamination. This improved method was also successfully applied to 14 other serotypes (1, 3, 4, 6A, 6B, 7F, 9V, 11A, 14, 18C, 19A, 19F, 22F, and 23F). To assess the immunogenicity of the CPS from the 15 serotypes, two sets of 15-valent pneumococcal conjugate vaccines were prepared using the previous purification method and the improved method developed here; these vaccines were administered to a rabbit model. Enzyme-linked immunosorbent assay and opsonophagocytic assay demonstrated higher immunogenicity of the conjugate vaccine prepared using CPS produced by the improved purification process.

Assignment of opsonic values to pneumococcal reference serum 007sp and a second pneumococcal OPA calibration serum panel (Ewha QC sera panel B) for 11 serotypes.

Pneumococcal conjugate vaccines (PCVs) have been effective in reducing the disease burden caused by Streptococcus pneumoniae. The first licensed PCV (PCV7) was composed of capsular polysaccharides from seven serotypes. This was followed by PCV10, then PCV13, and currently there are a number of higher valency vaccines in development. As part of licensure, new vaccine iterations require assessment of immunogenicity. Since some antibodies can be non-functional, measuring functional antibodies is desirable. To meet this need, opsonophagocytic assays (OPAs) have been developed. Previous studies have shown there can be significant variations in OPA results from different laboratories. We have previously shown that standardizing OPA data using reference serum 007sp can decrease this variation. To extend this approach to additional serotypes, a panel of sera was tested by five laboratories using a multiplexed OPA for serotypes 2, 8, 9N, 10A, 11A, 12F, 15B, 17F, 20B, 22F, and 33F. Each sample was tested in five runs with 007sp tested three times in each run. Results were analyzed using a mixed effects ANOVA model. Standardization of the results significantly decreased the inter-laboratory variation for some serotypes. For serotypes 2, 8, and 11A, the variability was reduced by 40%, 45%, and 40%, respectively. For serotypes 12F, 17F, and 20B, the reductions were more modest (14%, 19%, and 24%, respectively). Standardization had little effect for the remaining serotypes. In many cases, the impact of normalization was blunted by the results from five sera that were collected after an extended post-vaccination interval. We have previously reported consensus values for 007sp for 13 serotypes, as well as the creation of a calibration serum panel ("Ewha Panel A"). Here, we report consensus values for 11 additional serotypes for 007sp and the creation of a second serum panel ("Ewha Panel B"). These consensus values will facilitate the development of next-generation PCVs.

A randomized, non-inferiority trial comparing two bivalent killed, whole cell, oral cholera vaccines (Euvichol vs Shanchol) in the Philippines.

BACKGROUND: Currently, there are two oral cholera vaccines (OCV) that are prequalified by the World Health Organization. Both (Dukoral and Shanchol) have been proven to be safe, immunogenic, and effective. As the global supply of OCV remains limited, we assessed the safety and immunogenicity of a new low cost, killed, bivalent OCV (Euvichol) in the Philippines. METHODS: The randomized controlled trial was carried out in healthy Filipino adults and children. Two doses of either the current WHO prequalified OCV (Shanchol) or the same composition OCV being considered for WHO prequalification (Euvichol) were administered to participants. RESULTS: The pivotal study was conducted in total of 1263 healthy participants (777 adults and 486 children). No serious adverse reactions were elicited in either vaccine groups. Vibriocidal antibody responses to V. cholerae O1 Inaba following administration of two doses of Euvichol were non-inferior to those of Shanchol in adults (82% vs 76%) and children (87% vs 89%). Similar findings were observed for O1 Ogawa in adults (80% vs 74%) and children (91% vs 88%). CONCLUSION: A two dose schedule with Euvichol induces a strong vibriocidal response comparable to those elicited by the currently WHO prequalified OCV, Shanchol. Euvichol will be an oral cholera vaccine suitable for use in lower income countries, where cholera still has a significant economic and public health impact.