Immunogenicity and safety of heterologous Omicron BA.1 and bivalent SARS-CoV-2 recombinant spike protein booster vaccines: a phase 3, randomized, clinical trial.

BACKGROUND: Mutations present in emerging SARS-CoV-2 variants permit evasion of neutralization with prototype vaccines. A novel Omicron BA.1 subvariant-specific vaccine (NVX-CoV2515) was tested alone, or as a bivalent preparation in combination with the prototype vaccine (NVX-CoV2373), to assess antibody responses to SARS-CoV-2. METHODS: Participants aged 18 to 64 years immunized with 3 doses of prototype mRNA vaccines were randomized 1:1:1 to receive a single dose of NVX-CoV2515, NVX-CoV2373, or bivalent mixture in a phase 3 study investigating heterologous boosting with SARS-CoV-2 recombinant spike protein vaccines. Immunogenicity was measured 14 and 28 days after vaccination for the SARS-CoV-2 Omicron BA.1 sublineage and ancestral strain. Safety profiles of vaccines were assessed. RESULTS: Of participants who received trial vaccine (N = 829), those administered NVX-CoV2515 (n = 286) demonstrated superior neutralizing antibody response to BA.1 versus NVX-CoV2373 (n = 274) at Day 14 (geometric mean titer ratio [95% CI]: 1.6 [1.33, 2.03]). Seroresponse rates [n/N; 95% CI] were 73.4% [91/124; 64.7, 80.9] for NVX-CoV2515 versus 50.9% [59/116; 41.4, 60.3] for NVX-CoV2373. All formulations were similarly well-tolerated. CONCLUSIONS: NVX-CoV2515 elicited a superior neutralizing antibody response against the Omicron BA.1 subvariant compared with NVX-CoV2373 when administered as a fourth dose. Safety data were consistent with the established safety profile of NVX-CoV2373.

COVID-19 Vaccine Seroresponse Based on The Timing of The Primary Series; Pre- versus Post-Renal Transplantation.

BACKGROUND: Coronavirus disease 2019 (COVID-19) poses a serious risk to patients with chronic kidney disease (CKD) and renal transplant. While COVID-19 vaccination is recommended before transplant, there are limited data comparing vaccine timing. Our aim is to evaluate serological responses to COVID-19 vaccines pre- and post-renal transplant and the durability of antibody levels. METHODS: We retrospectively evaluated the antibody response of adult renal transplant recipients who had received at least a primary series of the COVID-19 vaccine. The patients were divided into two groups based on the timing; pre- or post-transplant. Antibody titer levels were evaluated at least 4 weeks after vaccination for each group. Titer durability was assessed by calculating the median titer level of individuals. RESULTS: A total of 139 patients were identified between January 2019 and April 2022. Twenty-nine patients were excluded because of previous COVID-19 infection, and 15 patients were excluded each for insufficient vaccine doses and lack of titer data. Forty patients were included for the pre-transplant group and 40 for post-transplant. The number of pre-transplant patients who developed antibodies (39 patients, 97.5%) was significantly greater than the number of post-transplant patients (21 patients, 52.5%) with p < .01. The median post-vaccination titer levels were significantly greater in the pre-transplant group up to 5 months after vaccination (p < .05). The pre-transplant group's titers seemed sustained even after renal transplantation. CONCLUSION: Vaccinating renal transplant patients before transplant results in increased achievement of seroresponse, higher levels of antibody titers, and sustained titers following transplant. Larger and prospective studies are warranted to confirm the findings.

Assessment of Mumps Virus-Specific Antibodies: Comparison of Plaque Reduction Neutralization Test and Enzyme-Linked Immunosorbent Assay Estimates.

BACKGROUND: The plaque reduction neutralization test (PRNT), which measures a subset of immunoglobulin antibodies (functional neutralizing antibodies), and the enzyme-linked immunosorbent assay (ELISA), which measures total immunoglobulin (neutralizing and nonneutralizing antibodies), characterize different aspects of the anti-mumps virus antibody response after vaccination. METHODS: Data from a recent phase 3 clinical trial (NCT01681992) of 2 measles-mumps-rubella vaccines were used to compare anti-mumps antibody responses measured using an unenhanced PRNT (GSK; seropositivity cutoff and threshold, 2.5 and 4 times the 50% end-point dilution, respectively) with those estimated using an ELISA (thresholds, 5 and 10 ELISA units/mL, respectively). RESULTS: Of 3990 initially seronegative samples, 3284 (82.3%) were seropositive after vaccination for anti-mumps antibodies in both assays. The Pearson correlation coefficient for double-positive samples was 0.57, indicative of a moderate correlation. Receiver operating characteristic curve analysis showed that an ELISA threshold of 51.7 ELISA units/mL best corresponded to the PRNT seroresponse threshold. There was no obvious vaccine brand effect on the correlation between assays. CONCLUSIONS: The moderate correlation between the anti-mumps antibody measurements obtained with PRNT and ELISA reflects different aspects of the serological response. In the absence of a well-defined protective serological threshold, PRNT provides complementary information on the antibody response, whereas ELISA remains a critically useful measurement of vaccine immunogenicity.

Combined immunogenicity evaluation for a new single-dose live-attenuated chikungunya vaccine.

BACKGROUND: Chikungunya is a serious and debilitating viral infection with a significant disease burden. VLA1553 (IXCHIQ®) is a live-attenuated vaccine licensed for active immunization for prevention of disease caused by chikungunya virus (CHIKV). METHODS: Immunogenicity following a single dose of VLA1553 was evaluated in healthy adults aged ≥18 years in two Phase 3 trials (N = 656 participants [per protocol analysis set]). Immunogenicity data to 180 days post-vaccination (geometric mean titers [GMTs], seroresponse rate, seroconversion rate) were pooled for the two trials. A comparison of subgroups based on age, sex, body mass index (BMI), race, and baseline seropositivity was included. All analyses were descriptive. RESULTS: Most participants were aged 18-64 years (N = 569/656 [86.7%]), there were slightly more females (N = 372/656 [56.7%]), most were not Hispanic/Latino (N = 579/656 [88.3%]), and most were White (N = 517/656 [78.8%]). In baseline seronegative participants, GMT peaked at Day 29 post-vaccination, and subsequently declined slightly but remained elevated until Day 180. At Days 29, 85, and 180, seroresponse rate was 98.3%, 97.7%, and 96.4% and seroconversion rate was 98.5%, 98.4%, and 98.2%. There were no differences in seroresponse rate in participants aged 18-64 years or ≥ 65 years at Day 29 (98.1% versus 100%), Day 85 (97.4% versus 100%), and Day 180 (96.3% versus 96.5%) nor based on sex, BMI, ethnicity, or race. An immune response was shown in a small heterogenous population of baseline seropositive participants, with GMTs showing the same trend as baseline seronegative participants. CONCLUSIONS: A single dose of VLA1553 elicited a very strong immune response by Day 29 that remained elevated at Day 180 in both baseline seronegative and seropositive participants in a combined evaluation of two Phase 3 trials. The vaccine was similarly immunogenic in participants aged ≥65 years and 18-64 years, and there were no differences based on subgroup analyses for sex, BMI, ethnicity, or race.

Seroprevalence of varicella-zoster virus antibody and immunogenicity of live attenuated varicella vaccine in healthcare workers in Taiwan.

BACKGROUND: Healthcare workers (HCWs) without evidence of immunity to varicella-zoster virus (VZV) are recommended to undergo varicella vaccination. Immunogenicity of live attenuated varicella vaccine has rarely been investigated among HCWs in Taiwan. METHODS: Anti-VZV immunoglobulin G (IgG) titer was checked for all HCWs at Changhua Christian Hospital from 2011 to 2017. One-dose and two-dose (separated by 4-8 weeks) vaccines were administered to HCWs with equivocal and negative anti-varicella IgG results, respectively. Follow-up anti-VZV IgG was determined at least 4 weeks after completion of vaccination. Factors associated with seroconversion to varicella vaccination were analyzed. RESULTS: Among 2406 included HCWs, the anti-VZV IgG serostatus was tested positive, equivocal and negative in 1924 (79.9%), 117 (4.9%) and 365 (15.2%), respectively. The seroprevalence had decreased from 88.0% (235/267) in 2011 to 72.2% (270/374) in 2017 (p for trend <0.05). A total of 67.8% (327/482) HCWs completed scheduled vaccination and serological follow-up. The seroconversion rates for HCWs with baseline equivocal and negative anti-VZV IgG results were 100% (80/80) and 79.4% (196/247) after one- and two-dose vaccination, respectively. In multivariate analysis, obesity (adjusted odds ratio, 0.308; 95% confidence interval [CI], 0.11-0.94, p = 0.039) was the only factor statistically significantly associated with seroconversion to vaccination. CONCLUSION: Decreasing trends of seroprevalence of VZV were observed among HCWs from 2011 to 2017. HCWs who were obese were less likely to respond to varicella vaccination.

Serial SARS-CoV-2 Antibody Titers in Vaccinated Dialysis Patients: Prevalence of Unrecognized Infection and Duration of Seroresponse.

Rationale & Objective: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections are likely underdiagnosed, but the degree of underdiagnosis among patients receiving maintenance dialysis is unknown. The durability of the immune response after the third vaccine dose in this population also remains uncertain. This descriptive study tracked antibody levels to (1) assess the rate of undiagnosed infections and (2) characterize seroresponse durability after the third dose. Study Design: Retrospective observational study. Setting & Participants: SARS-CoV-2-vaccinated patients receiving maintenance dialysis through a national dialysis provider. Immunoglobulin G spike antibodies [anti-spike immunoglobulin (Ig) G] titers were assessed monthly after vaccination. Exposures: Two and 3 doses of SARS-CoV-2 vaccine. Outcomes: Undiagnosed and diagnosed SARS-CoV-2 infections; anti-spike IgG titers over time. Analytical Approach: Undiagnosed SARS-CoV-2 infections were identified as an increase in anti-spike IgG titer of ≥100 BAU/mL, not associated with receipt of vaccine or diagnosed SARS-CoV-2 infection (by polymerase chain reaction test or antigen test). In descriptive analyses, anti-spike IgG titers were followed over time. Results: Among 2,703 patients without previous coronavirus disease 2019 (COVID-19) who received an initial 2-dose vaccine series, 271 had diagnosed SARS-CoV-2 infections (3.4 per 10,000 patient-days) and 129 had undiagnosed SARS-CoV-2 infections (1.6 per 10,000 patient-days). Among 1,894 patients without previous COVID-19 who received a third vaccine dose, 316 had diagnosed SARS-CoV-2 infections (7.0 per 10,000 patient-days) and 173 had undiagnosed SARS-CoV-2 infections (3.8 per 10,000 patient-days). In both cohorts, anti-spike IgG levels declined over time. Of the initial 2-dose cohort, 66% had a titer of ≥500 BAU/mL in the first month, with 24% maintaining a titer of ≥500 BAU/mL at 6 months. Of the third dose cohort, 95% had a titer of ≥500 BAU/mL in the first month after the third dose, with 77% maintaining a titer of ≥500 BAU/mL at 6 months. Limitations: The assays used had upper limits. Conclusions: Among patients receiving maintenance dialysis, about 1 in every 3 SARS-CoV-2 infections was undiagnosed. Given this population's vulnerability to COVID-19, ongoing infection control measures are needed. A 3-dose primary mRNA vaccine series optimizes seroresponse rate and durability. Plain-Language Summary: Patients receiving maintenance dialysis have been particularly vulnerable to COVID-19. Using serially measured antibodies, we found that a substantial proportion (about one-third) of SARS-CoV-2 infections among this population had been missed, both among those who had completed a 2-dose vaccine series and among those who had received a third vaccine dose. Such missed infections likely had only mild or minimal symptoms, but this failure to recognize all infections is concerning. Furthermore, vaccines have been effective among patients receiving dialysis, but our study additionally shows that the immune response wanes over time, even after a third dose. There is therefore a role for ongoing vigilance against this highly transmissible infection.

Serostatus cutoff levels and fold increase to define seroresponse to recombinant vesicular stomatitis virus - Zaire Ebola virus envelope glycoprotein vaccine: An evidence-based analysis.

The recombinant vesicular stomatitis virus - Zaire Ebola virus envelope glycoprotein (rVSVΔG-ZEBOV-GP) vaccine is a live recombinant vesicular stomatitis virus (VSV) where the VSV G protein is replaced with ZEBOV-GP. To better understand the immune response after receiving the rVSVΔG-ZEBOV-GP vaccine, the current analyses evaluated different definitions of seroresponse that differentiate vaccine and placebo recipients enrolled in a placebo-controlled clinical trial (PREVAIL; NCT02344407) in which a subset of the study participants had elevated baseline titers. Alternative values for serostatus cutoff (SSCO; 200-500 EU/mL) and/or fold rise (two- to five-fold) were applied to compare their ability to distinguish between participants receiving rVSVΔG-ZEBOV-GP or placebo. The results indicate that an SSCO of 200 EU/mL can be used to define seropositivity at baseline (i.e. pre-vaccination). The use of dual criteria of the same SSCO (200 EU/mL) together with a two-fold rise in antibody level from baseline provided the definition of seroresponse that maximized the statistical significance between vaccine recipients and placebo recipients post-vaccination. Clinical trial registration: NCT02344407.

Live attenuated tetravalent (G1-G4) bovine-human reassortant rotavirus vaccine (BRV-TV): Randomized, controlled phase III study in Indian infants.

BACKGROUND: Rotavirus remains the leading cause of diarrhoea among children <5years. We assessed immunogenic non-inferiority of a tetravalent bovine-human reassortant rotavirus vaccine (BRV-TV) over the licensed human-bovine pentavalent rotavirus vaccine RV5. METHODS: Phase III single-blind study (parents blinded) in healthy infants randomized (1:1) to receive three doses of BRV-TV or RV5 at 6-8, 10-12, and 14-16weeks of age. All concomitantly received a licensed diphtheria, tetanus, pertussis, hepatitis B, Haemophilus influenzae type b conjugate vaccine (DTwP-HepB-Hib) and oral polio vaccine (OPV). Immunogenic non-inferiority was evaluated in terms of the inter-group difference in anti-rotavirus serum IgA seroresponse (primary endpoint), and seroprotection/seroresponse rates to DTwP-HepB-Hib and OPV vaccines. Seroresponse was defined as a ≥4-fold increase in titers from baseline to D28 post-dose 3. Non-inferiority was declared if the difference between groups (based on the lower limit of the 95% confidence interval [CI]) was above -10%. Each subject was evaluated for solicited adverse events 7days and unsolicited & serious adverse events 28days following each dose of vaccination. RESULTS: Of 1195 infants screened, 1182 were randomized (590 to BRV-TV; 592 to RV5). Non-inferiority for rotavirus serum IgA seroresponse was not established: BRV-TV, 47.1% (95%CI: 42.8; 51.5) versus RV5, 61.2% (95%CI: 56.8; 65.5); difference between groups, -14.08% (95%CI: -20.4; -7.98). Serum IgA geometric mean concentrations at D28 post-dose 3 were 28.4 and 50.1U/ml in BRV-TV and RV5 groups, respectively. For all DTwP-HepB-Hib and OPV antigens, seroprotection/seroresponse was elicited in both groups and the -10% non-inferiority criterion between groups was met. There were 16 serious adverse events, 10 in BRV-TV group and 6 in RV5 group; none were classified as vaccine related. Both groups had similar vaccine safety profiles. CONCLUSION: BRV-TV was immunogenic but did not meet immunogenic non-inferiority criteria to RV5 when administered concomitantly with routine pediatric antigens in infants.

Evaluation of vaccine seroresponse rates and adverse event rates through Bayesian and frequentist methods.

In the evaluation of vaccine seroresponse rates and adverse reaction rates, extreme test results often occur, with substantial adverse event rates of 0% and/or seroresponse rates of 100%, which has produced several data challenges. Few studies have used both the Bayesian and frequentist methods on the same sets of data that contain extreme test cases to evaluate vaccine safety and immunogenicity. In this study, Bayesian methods were introduced, and the comparison with frequentist methods was made based on practical cases from randomized controlled vaccine trials and a simulation experiment to examine the rationality of the Bayesian methods. The results demonstrated that the Bayesian non-informative method obtained lower limits (for extreme cases of 100%) and upper limits (for extreme cases of zero), which were similar to the limits that were identified with the frequentist method. The frequentist rate estimates and corresponding confidence intervals (CIs) for extreme cases of 0 or 100% always equaled and included 0 or 100%, respectively, whereas the Bayesian estimations varied depending on the sample size, with none equaling zero or 100%. The Bayesian method obtained more reasonable interval estimates of the rates with extreme data compared with the frequentist method, whereas the frequentist method objectively expressed the outcomes of clinical vaccine trials. The two types of statistical results are complementary, and it is proposed that the Bayesian and frequentist methods should be combined to more comprehensively evaluate clinical vaccine trials.

Evaluation of safety and immunogenicity of a live attenuated tetravalent (G1-G4) Bovine-Human Reassortant Rotavirus vaccine (BRV-TV) in healthy Indian adults and infants.

BACKGROUND: Rotavirus infections, prevalent in human populations worldwide are mostly caused by Group A viruses. Live attenuated rotavirus vaccines are highly effective in preventing severe rotavirus gastroenteritis. However, the cost of these vaccines and local availability can be a barrier for widespread adoption in public health programs in developing countries where infants suffer a heavy burden of rotavirus related morbidity and mortality. A phase I/II study was carried out with the long term aim to produce a locally licensed vaccine which is equally safe and immunogenic as compared to available licensed vaccines. METHODS: This study was conducted in two cohorts. In the first cohort, 20 healthy adults were administered a single dose of the rotavirus vaccine (highest antigen concentration planned for infants) or placebo and were followed up for 10 days for safety. Following demonstration of safety in adult volunteers, 100 healthy infants were recruited (cohort 2) and randomly divided into five equal study groups. They were administered three doses of either the investigational rotavirus vaccine (BRV-TV) at one of the three antigen concentrations or Rotateq or Placebo at 6-8, 10-12 and 14-16 weeks of age. All infants were followed up for safety till 28 days after the third dose. Immune response to the vaccine, in terms of seroresponse and geometric mean concentrations, was compared across the five study groups. RESULTS: Increase in anti-rotavirus serum IgA antibodies from baseline, demonstrated higher immune response for all the three antigen concentrations of BRV-TV vaccine and RotaTeq in comparison with the placebo. Sero-response rates for placebo, BRV-TV dose-levels 10(5.0) FFU, 10(5.8) FFU, 10(6.4) FFU, and Rotateq at 28 days post third dose were 11.1%, 27.8%, 41.2%, 83.3%, and 63.2% respectively using the four-fold or more criteria. The BRV-TV vaccine arm corresponding to the highest antigen concentration of 10(6.4) FFU had a higher sero-response rate compared to the active comparator arm (RotaTeq), 28 days post each vaccine dose. The safety profile was comparable across the treatment groups. CONCLUSIONS: Overall, the results showed that all three doses of BRV-TV vaccine were safe, well tolerated and displayed good immunogenicity (dose-response) in healthy Indian infants.