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The recombinant, live, attenuated, tetravalent dengue vaccine CYD-TDV has shown efficacy against all four dengue serotypes. In this exploratory study (CYD59, NCT02827162), we evaluated potential associations of host human leukocyte antigen (HLA) alleles with dengue antibody responses, CYD-TDV vaccine efficacy, and virologically-confirmed dengue (VCD) cases. Children 4-11 years old, who previously completed a phase 2b efficacy study of CYD-TDV in a single center in Thailand, were included in the study. Genotyping of HLA class I and II loci was performed by next-generation sequencing from DNA obtained from 335 saliva samples. Dengue neutralizing antibody titers (NAb) were assessed as a correlate of risk and protection. Regression analyses were used to assess associations between HLA alleles and NAb responses, vaccine efficacy, and dengue outcomes. Month 13 NAb log geometric mean titers (GMTs) were associated with decreased risk of VCD. In the vaccine group, HLA-DRB1*11 was significantly associated with higher NAb log GMT levels (beta: 0.76; p = 0.002, q = 0.13). Additionally, in the absence of vaccination, HLA associations were observed between the presence of DPB1*03:01 and increased NAb log GMT levels (beta: 1.24; p = 0.005, q = 0.17), and between DPB1*05:01 and reduced NAb log GMT levels (beta: -1.1; p = 0.001, q = 0.07). This study suggests associations of HLA alleles with NAb titers in the context of dengue outcomes. This study was registered with clinicaltrials.gov: NCT02827162., Competing Interests: Declaration of Competing Interest D.C., C.F., A.B., F.B., S.G. are employees of Sanofi Pasteur and may hold shares and/or stock options in the company. R.T., K.L., W.H., S.S., W.T., R.G.J., A.G., A.S., P.E., N.L.M., C.B. have no conflict of interest to declare. P.B.G., Z.M., M.J., and S.S.L. received a contract from Sanofi Pasteur to conduct the statistical analysis work., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: CYD-TDV, a live, attenuated, tetravalent dengue vaccine, has been approved for the prevention of symptomatic dengue in previously dengue exposed individuals. This post hoc analysis assessed hospitalized and severe virologically confirmed dengue (VCD) over the complete 6-year follow-up of 3 CYD-TDV efficacy studies (CYD14, CYD15, and CYD23/CYD57)., Methods: The main outcomes were hazard ratios (HRs) for hospitalized or severe VCD by baseline dengue serostatus, focusing on those who were seropositive, and by age at immunization (<9 years/≥9 years). Baseline dengue serostatus was measured or inferred using several methods. Hospitalized VCD cases were characterized in terms of clinical signs and symptoms and wild-type viremia level. Antibody persistence was assessed up to 5 years after the last injection., Results: In those aged ≥9 years and baseline seropositive, CYD-TDV protected against hospitalized and severe VCD over 6 years compared to placebo (HR [95% confidence interval] multiple imputation from month 0 method, .19 [.12-.30] and .15 [.06-.39]; other methods were consistent). Vaccine protection was observed over the different study periods, being highest during the first 2 years. Evidence for a decreased risk of hospitalized and severe VCD was also observed in seropositive participants aged 6-8 years. Clinical signs and symptoms, and quantified dengue viremia from participants with hospitalized VCD were comparable between groups., Conclusions: CYD-TDV demonstrated robust protection against hospitalized and severe VCD over the entire 6-year follow-up in participants who were seropositive and ≥9 years old. Protection was also observed in seropositive 6-8 year-olds. Clinical Trials Registration: NCT00842530, NCT01983553, NCT01373281, NCT01374516., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.)

The tetravalent dengue vaccine (CYD-TDV) is approved for use as a 3-dose series for the prevention of dengue in seropositive individuals ≥9 years. A randomized, placebo-controlled, phase II study of a booster dose of CYD-TDV in individuals who completed the 3-dose schedule >5 years previously (NCT02824198), demonstrated that a booster restored neutralizing antibody titers to post-dose 3 levels. We present additional immunogenicity assessments up to 24 months post-booster, and B- and T-cell responses in a participant subset. Participants aged 9-45 years that had received all three doses of CYD-TDV were randomized 3:1 to receive a booster dose of CYD-TDV (n = 89) or placebo (n = 29). Neutralizing antibody levels at Months 1, 6, 12, and 24 post-booster were assessed by plaque reduction neutralization test. In a subset, B-cell responses were assessed by a fluorescent immunospot assay, and T-cells analyzed by flow cytometry at Days 0, 7, 12, Months 1 and 12. We observed an increase of antibody titers Month 1 post-booster, then a gradual decline to Month 24. In the CYD-TDV booster group, an increase in plasmablasts was seen at Day 7 declining by Day 14, an increase in memory B-cells was observed at Day 28 with no persistence at Month 12. CYD-TDV booster recalled a CD8+ T-cell response, dominated by IFN-γ secretion, which decreased 12 months post-booster. This study showed a short-term increase in antibody titers and then gradual decrease following CYD-TDV booster injection >5 years after primary immunization, and the presence of memory B-cells activated following the booster, but with low persistence.

A simplified dose regimen of the live, attenuated, tetravalent dengue vaccine (CYD-TDV) could have the potential to facilitate easier implementation of immunization programs against symptomatic virologically-confirmed dengue (VCD) in dengue seropositive individuals aged ≥ 9 years. This post-hoc analysis of two Phase III studies (CYD14 [NCT01373281] and CYD15 [NCT01374516]) in dengue endemic areas assessed the efficacy of CYD-TDV by dengue serostatus between dose 1 and 2 (at Month [M] 6), between dose 2 and 3 (at M12), and from dose 3 to M25. Baseline dengue serostatus (seropositive or seronegative) was determined based on measured dengue neutralizing antibody titers with the 50% plaque reduction neutralization test (PRNT 50 ) or ascertained by logistic regression-based multiple imputation (MI) to predict PRNT 50 . Vaccine efficacy against symptomatic VCD was assessed by age and baseline dengue serostatus using a case-cohort framework. Dengue neutralizing antibody geometric mean titers (GMTs) were measured with the PRNT 50 at 28 days post-dose 2 and 3. Vaccine efficacy estimates in seropositive participants aged ≥ 9 years at post-dose 1, 2, and 3 were 80.5% (95% CI, 66.2, 88.7), 82.0% (95% CI, 70.5, 89.0), and 75.2% (95% CI, 65.9, 81.9), respectively. In seropositive participants aged < 9 years, vaccine efficacy estimates were 48.5% (95% CI, -24.3, 78.6), 68.3% (95% CI, 34.5, 84.7), and 65.3% (95% CI, 40.2, 79.9), respectively. CYD-TDV efficacy was null to modest after any dose in seronegative participants, regardless of age group. Seropositive participants aged ≥ 9 years in the CYD-TDV group had GMTs post-dose 3 that did not exceed those observed post-dose 2. In conclusion, CYD-TDV has high efficacy against VCD from the first dose through to M25, with estimates at post-dose 1 and 2 similar to or higher than those at post-dose 3 in seropositive participants aged ≥ 9 years, consistent with immunogenicity data., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. GHD, EL, BZ, RF, BZ, FN, CF, TM, SS, and CADG are employees at Sanofi Pasteur. AB was an employee of Sanofi Pasteur at the time of the study was undertaken but is no longer affiliated with the company., (Copyright © 2020. Published by Elsevier Ltd.)

CYD-TDV is a live, attenuated, tetravalent dengue vaccine licensed in 21 countries. We undertook a post-hoc analysis of the long-term efficacy of CYD-TDV during the surveillance expansion phase (SEP) of two Phase III studies (CYD14 in the Asia-Pacific region; CYD15 in Latin America). The SEP included approximately Year 5 and the entire Year 6 of follow-up after the first study injection. Vaccine efficacy against symptomatic virologically-confirmed dengue (VCD) was assessed by participant age (any age, ≥9, <9, 2-5, and 6-8 years at the time of the first injection) and baseline dengue serostatus using a case-cohort framework. Baseline dengue serostatus was estimated by several methods including logistic regression-based multiple imputation (MI) to predict PRNT 50 with key predictor being Month 13 (M13) anti-non-structural protein (NS1) titers; superlearner-based imputation by targeted minimum loss based estimation (TMLE); and M13 anti-NS1 titer threshold 9 EU/mL (NS1 M13). There were 436 symptomatic VCD cases (CYD14: n = 360; CYD15: n = 76) during the SEP. Vaccine efficacy in seropositive participants aged ≥9 years was assessed by MI (47.9% [95% CI 19.4; 66.3]), TMLE (53.0% [95% CI 23; 71]), and NS1 M13 (52.4% [95% CI 30.8; 67.3]). Vaccine efficacy estimates were lower in seropositive individuals aged <9 years compared with individuals ≥9 years. Among seropositive individuals aged 2-5 and 6-8 years, vaccine efficacy across the different approaches for assessing serostatus ranged from between -25.7 to 36.9% and 44.4 to 64.7% during the SEP, respectively. In the pooled CYD14/15 data of seronegatives, vaccine efficacy was null to modest. In conclusion, CYD-TDV was shown to maintain efficacy against symptomatic VCD in seropositive participants aged ≥9 years up to six years after the first dose. Persistence of efficacy was also observed in seropositive participants aged 6-8 years., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Sanofi Pasteur. Published by Elsevier Ltd.. All rights reserved.)

The tetravalent dengue vaccine (CYD-TDV; Dengvaxia®) is administered on a three-dose schedule, 6 months apart in those aged ≥9 years in a number of dengue-endemic countries in Asia and Latin America. In this study, CYD63 (NCT02824198), participants aged 9-45 years at first vaccination, and who had received three doses of CYD-TDV in the CYD28 study more than 5 years previously, were randomized 3:1 to receive a booster CYD-TDV dose (Group 1) or placebo (Group 2). Dengue neutralizing antibody geometric mean titres (PRNT 50 GMTs) for each of the four dengue serotypes were assessed in sera collected before and 28 days after booster injections. Non-inferiority of the booster immune response versus that induced after the third dose was demonstrated for each serotype if the lower limit of the two-sided 95% confidence interval (CI) was >0.5 for the GMT ratios (GMTRs) between post-booster CYD-TDV dose and post-dose 3 in Group 1. Overall, 118 participants received CYD-TDV booster or placebo and 116 (98.3%) completed the study; two participants were withdrawn because of noncompliance. GMTs in the booster CYD-TDV group increased across all serotypes post-booster injection by 1.74- (serotype 1) to 3.58-fold (serotype 4). No discernible increases were observed in the placebo group. Non-inferiority was demonstrated for serotypes 1, 3, and 4, but not for serotype 2 (GMTR; 0.603 [95% CI, 0.439- 0.829]). No safety issues were observed. These data show that the CYD-TDV booster given 5 or more years later tended to restore GMTs back to levels observed post-dose 3.

The CYD-TDV vaccine is licensed in multiple endemic countries based on vaccine efficacy (VE) against symptomatic, virologically confirmed dengue demonstrated in two phase 3 trials (CYD14, 2- to 14-year-olds, Asia; CYD15, 9- to 16-year-olds, Latin America). 50% plaque reduction neutralization test (PRNT 50 ) titers at baseline and month 13 (post-vaccination) were associated with VE and may enable bridging VE to adults. Two phase 2 trials of CYD-TDV measured baseline and month 13 PRNT 50 titers: CYD22 (9- to 45-year-olds, Vietnam) and CYD47 (18- to 45-year-olds, India). 50% plaque reduction neutralization test distributions were compared between age cohorts, and four versions of an epidemiological bridging method were used to estimate VE against any serotype (dengue virus [DENV]-Any) and against each serotype over 25 months post first vaccination in a hypothetical CYD14 + CYD15 18- to 45-year-old cohort (bridging population 1) and in the actual CYD47 18- to 45-year-old cohort (bridging population 2). Baseline and month 13 geometric mean PRNT 50 titers to each serotype were significantly greater in 18- to 45-year-olds than 9- to 16-year-olds for all comparisons. The four methods estimated VE against DENV-Any at 75.3-86.0% (95% CIs spanning 52.5-100%) for bridging population 1 and 68.4-77.5% (95% CIs spanning 42.3-88.5%) for bridging population 2. The vaccine efficacy against serotype 1, 2, 3, and 4 was estimated at 56.9-76.9%, 68.3-85.8%, 91.4-95.0%, and 93.2-100% (bridging population 1) and 44.5-66.9%, 53.2-69.2%, 79.8-92.0%, and 90.6-95.0% (bridging population 2), respectively; thus, CYD-TDV would likely confer improved efficacy in adults than 9- to 16-year-olds. Using the same methods, we predicted VE against hospitalized DENV-Any over 72 months of follow-up, with estimates 59.1-73.5% (95% CIs spanning 40.9-92.2%) for bridging population 1 and 50.9-65.9% (95% CIs spanning 38.1-82.1%) for bridging population 2.

Dengue is prevalent in the Asia-Pacific region. Participants of two immunogenicity and safety phase II studies conducted in Singapore and Vietnam (NCT0088089 and NCT00875524, respectively) were followed for up to four years after third vaccine dose of a recombinant, live, attenuated, tetravalent dengue vaccine (CYD-TDV). Participants (2-45 years) received three doses of CYD-TDV or control at 0, 6, and 12 months. Dengue plaque reduction neutralization test (PRNT 50 ) antibody titers were measured in both studies. Cytokine-producing antigen-specific CD4+ and CD8+ T-cells were quantified to assess cell-mediated immunity (CMI) in Singapore. Post-hoc analyses were carried out for participants aged <9 and ≥9 years old. Related and fatal serious adverse events (SAEs) were collected during long-term follow-up. Of participants who received ≥1 CYD-TDV injection in Singapore (n = 1198) and Vietnam (n = 180), 87% and 92% participants completed long-term follow-up, respectively. At four years, geometric mean titers (GMTs) in participants who received CYD-TDV ranged from 30.2 1/dil (95% CI 23.9-38.3) to 73.7 (49.3-110) 1/dil in Vietnam and 9.73 1/dil (95% CI 8.28-11.4) to 21.8 (18.9-25.1) 1/dil in Singapore. Interferon and interleukin-13 levels were lower at four years than one year post-vaccination but were still present. Tumor necrosis factor- α levels at four years were similar to those after the third vaccine dose. Seropositivity rates were higher at year four in participants who were seropositive vs. seronegative at baseline in both studies. No safety concerns were identified. CYD-TDV demonstrated long-term immunogenicity and was well-tolerated for four years after the third vaccine dose.

Background: In efficacy trials of a tetravalent dengue vaccine (CYD-TDV), excess hospitalizations for dengue were observed among vaccine recipients 2 to 5 years of age. Precise risk estimates according to observed dengue serostatus could not be ascertained because of the limited numbers of samples collected at baseline. We developed a dengue anti-nonstructural protein 1 (NS1) IgG enzyme-linked immunosorbent assay and used samples from month 13 to infer serostatus for a post hoc analysis of safety and efficacy., Methods: In a case-cohort study, we reanalyzed data from three efficacy trials. For the principal analyses, we used baseline serostatus determined on the basis of measured (when baseline values were available) or imputed (when baseline values were missing) titers from a 50% plaque-reduction neutralization test (PRNT 50 ), with imputation conducted with the use of covariates that included the month 13 anti-NS1 assay results. The risk of hospitalization for virologically confirmed dengue (VCD), of severe VCD, and of symptomatic VCD according to dengue serostatus was estimated by weighted Cox regression and targeted minimum loss-based estimation., Results: Among dengue-seronegative participants 2 to 16 years of age, the cumulative 5-year incidence of hospitalization for VCD was 3.06% among vaccine recipients and 1.87% among controls, with a hazard ratio (vaccine vs. control) through data cutoff of 1.75 (95% confidence interval [CI], 1.14 to 2.70). Among dengue-seronegative participants 9 to 16 years of age, the cumulative incidence of hospitalization for VCD was 1.57% among vaccine recipients and 1.09% among controls, with a hazard ratio of 1.41 (95% CI, 0.74 to 2.68). Similar trends toward a higher risk among seronegative vaccine recipients than among seronegative controls were also found for severe VCD. Among dengue-seropositive participants 2 to 16 years of age and those 9 to 16 years of age, the cumulative incidence of hospitalization for VCD was 0.75% and 0.38%, respectively, among vaccine recipients and 2.47% and 1.88% among controls, with hazard ratios of 0.32 (95% CI, 0.23 to 0.45) and 0.21 (95% CI, 0.14 to 0.31). The risk of severe VCD was also lower among seropositive vaccine recipients than among seropositive controls., Conclusions: CYD-TDV protected against severe VCD and hospitalization for VCD for 5 years in persons who had exposure to dengue before vaccination, and there was evidence of a higher risk of these outcomes in vaccinated persons who had not been exposed to dengue. (Funded by Sanofi Pasteur; ClinicalTrials.gov numbers, NCT00842530 , NCT01983553 , NCT01373281 , and NCT01374516 .).

Background: We previously reported that vaccination with the tetravalent dengue vaccine (CYD-TDV; Dengvaxia) may bias the diagnosis of dengue based on immunoglobulin M (IgM) and immunoglobulin G (IgG) assessments., Methods: We undertook a post hoc pooled analysis of febrile episodes that occurred during the active surveillance phase (the 25 months after the first study injection) of 2 pivotal phase III, placebo-controlled CYD-TDV efficacy studies that involved ≥31000 children aged 2-16 years across 10 countries in Asia and Latin America. Virologically confirmed dengue (VCD) episode was defined with a positive test for dengue nonstructural protein 1 antigen or dengue polymerase chain reaction. Probable dengue episode was serologically defined as (1) IgM-positive acute- or convalescent-phase sample, or (2) IgG-positive acute-phase sample and ≥4-fold IgG increase between acute- and convalescent-phase samples., Results: There were 1284 VCD episodes (575 and 709 in the CYD-TDV and placebo groups, respectively) and 17673 other febrile episodes (11668 and 6005, respectively). Compared with VCD, the sensitivity and specificity of probable dengue definition were 93.1% and 77.2%, respectively. Overall positive and negative predictive values were 22.9% and 99.5%, respectively, reflecting the much lower probability of correctly confirming probable dengue in a population including a vaccinated cohort. Vaccination-induced bias toward false-positive diagnosis was more pronounced among individuals seronegative at baseline., Conclusions: Caution will be required when interpreting IgM and IgG data obtained during routine surveillance in those vaccinated with CYD-TDV. There is an urgent need for new practical, dengue-specific diagnostic algorithms now that CYD-TDV is approved in a number of dengue-endemic countries., Clinical Trials Registration: NCT01373281 and NCT01374516.

Dengue seroprevalence data in the literature is limited and the available information is difficult to compare between studies because of the varying survey designs and methods used. We assessed dengue seropositivity across 14 countries using data from 15 trials conducted during the development of a tetravalent dengue vaccine between October 2005 and February 2014. Participants' dengue seropositivity (n=8592) was determined from baseline (before vaccination) serum samples at two centralized laboratories with the plaque reduction neutralization test (PRNT50). Seropositivity rates generally increased with age in endemic settings. Although seropositivity rates varied across geographical areas, between countries, and within countries by region, no major differences were observed for given age groups between the two endemic regions, Latin America and Asia-Pacific. Seropositivity rates were generally stable over time. The proportion of participants who had only experienced primary infection tended to be higher in younger children than adolescents/adults. These results will help inform and guide dengue control strategies in the participating countries.

Background: We assessed replication and excretion of the live attenuated tetravalent dengue vaccine (CYD-TDV) into biological fluids following vaccination in dengue-naive adults in Australia., Methods: Vaccinal viremia/shedding was assessed in a subset of participants enrolled in a lot-to-lot consistency study; 95 participants received 3 subcutaneous doses of CYD-TDV from phase 2/3 lots of the vaccine, and 8 received placebo; doses were administered 6 months apart. Quantitative reverse-transcription polymerase chain reaction (qR-PCR) analysis was used to initially detect the yellow fever virus (YFV) core protein gene in the backbone of CYD-TDV in serum, saliva and urine, followed by serotype-specific qRT-PCR analysis of samples positive for YFV by qRT-PCR (lower limit of detection, 5.16 GEq/mL)., Results: YFV viremia was detected by qRT-PCR in 69.5% of participants (66 of 95) who received CYD-TDV, mainly 6-14 days after injection 1. The serotypes detected were serotype 4 (in 68.2% of participants [45 of 95]), serotype 3 (in 19.7% [13 of 95]), and serotype 1 (in 12.1% [8 of 95]); serotype 2 was not detected. None of the placebo recipients had vaccinal viremia/shedding. No participants had detectable viral shedding into saliva at levels above the lower limit of quantitation. Two participants had low-level viral shedding (serotype 3) in urine (5.47 and 5.77 GEq/mL). None of the participants with viremia or shedding experienced concomitant fever., Conclusions: Low-level vaccinal viremia may occur following vaccination with CYD-TDV, but this is not associated with any symptom or adverse event., Clinical Trials Registration: NCT01134263., (© The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Dengue incidence has increased globally, but empirical burden estimates are scarce. Prospective methods are best-able to capture all severities of disease. CYD14 was an observer-blinded dengue vaccine study conducted in children 2-14 years of age in Indonesia, Malaysia, Thailand, the Philippines, and Vietnam. The control group received no vaccine and resembled a prospective, observational study. We calculated the rates of dengue according to different laboratory or clinical criteria to make inferences about dengue burden, and compared with rates reported in the passive surveillance systems to calculate expansion factors which describe under-reporting. Over 6,933 person-years of observation in the control group there were 319 virologically confirmed dengue cases, a crude attack rate of 4.6%/year. Of these, 92 cases (28.8%) were clinically diagnosed as dengue fever or dengue hemorrhagic fever by investigators and 227 were not, indicating that most symptomatic disease fails to satisfy existing case definitions. When examining different case definitions, there was an inverse relationship between clinical severity and observed incidence rates. CYD14's active surveillance system captured a greater proportion of symptomatic dengue than national passive surveillance systems, giving rise to expansion factors ranging from 0.5 to 31.7. This analysis showed substantial, unpredictable and variable under-reporting of symptomatic dengue, even within a controlled clinical trial environment, and emphasizes that burden estimates are highly sensitive to case definitions. These data will assist in generating disease burden estimates and have important policy implications when considering the introduction and health economics of dengue prevention and control interventions.

Background: Dengue diagnosis confirmation and surveillance are widely based on serological assays to detect anti-dengue IgM or IgG antibodies since such tests are affordable/user-friendly. The World Health Organization identified serological based diagnosis as a potential tool to define probable dengue cases in the context of vaccine trials, while acknowledging that this may have to be interpreted with caution., Methods: In a phase IIb randomized, placebo-controlled trial assessing the efficacy of a tetravalent dengue vaccine (CYD-TDV) in Thai schoolchildren, case definition was based on virological confirmation by either serotype-specific RT-PCRs or by NS1-antigen ELISA (Clinicaltrials.gov NCT00842530). Here, we characterized suspected dengue cases using IgM and IgG ELISA to assess their utility in evaluating probable dengue cases in the context of vaccine efficacy trials, comparing virologically-confirmed and serologically diagnosed dengue in the vaccine and placebo groups. Serologically probable cases were defined as: (1) IgM positive acute- or convalescent-phase samples, or (2) IgG positive acute-phase sample and ≥4-fold IgG increase between acute and convalescent-phase samples., Results: Serological diagnosis had good sensitivity (97.1%), but low specificity (85.1%) compared to virological confirmation. A high level of false positivity through serology diagnosis particularly in the 2 months post-vaccination was observed, and is most likely related to detection of the immune response to the dengue vaccine. This lack of specificity and bias with vaccination demonstrates the limitation of using IgM and IgG antibody responses to explore vaccine efficacy., Conclusion: Reliance on serological assessments would lead to a significant number of false positives during routine clinical practice and surveillance following the introduction of the dengue vaccine., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Dengue is a mosquito-borne viral disease that is endemic in India. We evaluated the immunogenicity and safety of recombinant, live-attenuated, tetravalent dengue vaccine (CYD-TDV) in Indian adults. In this observer-blind, randomized, placebo-controlled, Phase II study, adults aged 18-45 years were randomized 2:1 to receive CYD-TDV or placebo at 0, 6 and 12 months in sub-cutaneous administration. Immunogenicity was assessed using a 50% plaque reduction neutralization test (PRNT50) at baseline and 28 days after each study injection. 189 participants were enrolled (CYD-TDV [n = 128]; placebo, [n = 61]). At baseline, seropositivity rates for dengue serotypes 1, 2, 3 and 4 ranged from 77.0% to 86.9%. Seropositivity rates for each serotype increased after each CYD-TDV injection with a more pronounced increase after the first injection. In the CYD-TDV group, geometric mean titres (GMTs) were 2.38 to 6.11-fold higher after the third injection compared with baseline but remained similar to baseline in the placebo group. In the CYD-TDV group, the GMTs were 1.66 to 4.95-fold higher and 9.23 to 24.6-fold higher after the third injection compared with baseline in those who were dengue seropositive and dengue seronegative, respectively. Pain was the most commonly reported solicited injection site reaction after the first injection in both the CYD-TDV (6.3%) and placebo groups (4.9%), but occurred less frequently after subsequent injections. No serious adverse events were vaccine-related, no immediate unsolicited adverse events, and no virologically-confirmed cases of dengue, were reported during the study. The immunogenicity and safety of CYD-TDV was satisfactory in both dengue seropositive and seronegative Indian adults.

Background: A candidate tetravalent dengue vaccine is being assessed in three clinical trials involving more than 35,000 children between the ages of 2 and 16 years in Asian-Pacific and Latin American countries. We report the results of long-term follow-up interim analyses and integrated efficacy analyses., Methods: We are assessing the incidence of hospitalization for virologically confirmed dengue as a surrogate safety end point during follow-up in years 3 to 6 of two phase 3 trials, CYD14 and CYD15, and a phase 2b trial, CYD23/57. We estimated vaccine efficacy using pooled data from the first 25 months of CYD14 and CYD15., Results: Follow-up data were available for 10,165 of 10,275 participants (99%) in CYD14 and 19,898 of 20,869 participants (95%) in CYD15. Data were available for 3203 of the 4002 participants (80%) in the CYD23 trial included in CYD57. During year 3 in the CYD14, CYD15, and CYD57 trials combined, hospitalization for virologically confirmed dengue occurred in 65 of 22,177 participants in the vaccine group and 39 of 11,089 participants in the control group. Pooled relative risks of hospitalization for dengue were 0.84 (95% confidence interval [CI], 0.56 to 1.24) among all participants, 1.58 (95% CI, 0.83 to 3.02) among those under the age of 9 years, and 0.50 (95% CI, 0.29 to 0.86) among those 9 years of age or older. During year 3, hospitalization for severe dengue, as defined by the independent data monitoring committee criteria, occurred in 18 of 22,177 participants in the vaccine group and 6 of 11,089 participants in the control group. Pooled rates of efficacy for symptomatic dengue during the first 25 months were 60.3% (95% CI, 55.7 to 64.5) for all participants, 65.6% (95% CI, 60.7 to 69.9) for those 9 years of age or older, and 44.6% (95% CI, 31.6 to 55.0) for those younger than 9 years of age., Conclusions: Although the unexplained higher incidence of hospitalization for dengue in year 3 among children younger than 9 years of age needs to be carefully monitored during long-term follow-up, the risk among children 2 to 16 years of age was lower in the vaccine group than in the control group. (Funded by Sanofi Pasteur; ClinicalTrials.gov numbers, NCT00842530, NCT01983553, NCT01373281, and NCT01374516.).

Background: The recombinant yellow fever-17D-dengue virus, live, attenuated, tetravalent dengue vaccine (CYD-TDV) has undergone extensive clinical trials. Here safety and consistency of immunogenicity of phase III manufacturing lots of CYD-TDV were evaluated and compared with a phase II lot and placebo in a dengue-naïve population., Methods: Healthy 18-60 year-olds were randomly assigned in a 3:3:3:3:1 ratio to receive three subcutaneous doses of either CYD-TDV from any one of three phase III lots or a phase II lot, or placebo, respectively in a 0, 6, 12 month dosing schedule. Neutralising antibody geometric mean titres (PRNT50 GMTs) for each of the four dengue serotypes were compared in sera collected 28 days after the third vaccination-equivalence among lots was demonstrated if the lower and upper limits of the two-sided 95% CIs of the GMT ratio were ≥0.5 and ≤2.0, respectively., Results: 712 participants received vaccine or placebo and 614 (86%) completed the study; 17 (2.4%) participants withdrew after adverse events. Equivalence of phase III lots was demonstrated for 11 of 12 pairwise comparisons. One of three comparisons for serotype 2 was not statistically equivalent. GMTs for serotype 2 in phase III lots were close to each other (65.9, 44.1 and 58.1, respectively)., Conclusions: Phase III lots can be produced in a consistent manner with predictable immune response and acceptable safety profile similar to previously characterised phase II lots. The phase III lots may be considered as not clinically different as statistical equivalence was shown for serotypes 1, 3 and 4 across the phase III lots. For serotype 2, although equivalence was not shown between two lots, the GMTs observed in the phase III lots were consistently higher than those for the phase II lot. As such, in our view, biological equivalence for all serotypes was demonstrated., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: An estimated 100 million people have symptomatic dengue infection every year. This is the first report of a phase 3 vaccine efficacy trial of a candidate dengue vaccine. We aimed to assess the efficacy of the CYD dengue vaccine against symptomatic, virologically confirmed dengue in children., Methods: We did an observer-masked, randomised controlled, multicentre, phase 3 trial in five countries in the Asia-Pacific region. Between June 3, and Dec 1, 2011, healthy children aged 2-14 years were randomly assigned (2:1), by computer-generated permuted blocks of six with an interactive voice or web response system, to receive three injections of a recombinant, live, attenuated, tetravalent dengue vaccine (CYD-TDV), or placebo, at months 0, 6, and 12. Randomisation was stratified by age and site. Participants were followed up until month 25. Trial staff responsible for the preparation and administration of injections were unmasked to group allocation, but were not included in the follow-up of the participants; allocation was concealed from the study sponsor, investigators, and parents and guardians. Our primary objective was to assess protective efficacy against symptomatic, virologically confirmed dengue, irrespective of disease severity or serotype, that took place more than 28 days after the third injection. The primary endpoint was for the lower bound of the 95% CI of vaccine efficacy to be greater than 25%. Analysis was by intention to treat and per procotol. This trial is registered with ClinicalTrials.gov, number NCT01373281., Findings: We randomly assigned 10,275 children to receive either vaccine (n=6851) or placebo (n=3424), of whom 6710 (98%) and 3350 (98%), respectively, were included in the primary analysis. 250 cases of virologically confirmed dengue took place more than 28 days after the third injection (117 [47%] in the vaccine group and 133 [53%] in the control group). The primary endpoint was achieved with 56·5% (95% CI 43·8-66·4) efficacy. We recorded 647 serious adverse events (402 [62%] in the vaccine group and 245 [38%] in the control group). 54 (1%) children in the vaccine group and 33 (1%) of those in the control group had serious adverse events that happened within 28 days of vaccination. Serious adverse events were consistent with medical disorders in this age group and were mainly infections and injuries., Interpretation: Our findings show that dengue vaccine is efficacious when given as three injections at months 0, 6, and 12 to children aged 2-14 years in endemic areas in Asia, and has a good safety profile. Vaccination could reduce the incidence of symptomatic infection and hospital admission and has the potential to provide an important public health benefit., Funding: Sanofi Pasteur., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Unlabelled: Several ChimeriVax-Dengue (CYD)-based vaccination strategies were investigated as potential alternatives to vaccination with tetravalent CYD vaccine (CYD-TDV) in this phase IIa trial conducted in 2008-9 in 150 healthy adults. Participants were randomized and vaccinated on D0 and D105 (± 15 days). One group received bivalent CYD vaccine against serotypes 1 and 3 (CYD-1;3) on day 0 and CYD-2;4 on day 105 (± 15 days). Two groups received an injection at each timepoint of a tetravalent blend of CYD-1;3;4 and a VERO cell derived, live attenuated vaccine against serotype 2 (VDV-2), or the reference CYD-TDV. A fourth group received Japanese encephalitis (JE) vaccine on days -14, -7 and 0, followed by CYD-TDV on day 105. Viraemia was infrequent in all groups. CYD-4 viraemia was most frequent after tetravalent vaccination, while CYD-3 viraemia was most frequent after the first bivalent vaccination. Immunogenicity as assessed by 50% plaque reduction neutralisation test on D28 was comparable after the first injection of either tetravalent vaccine, and increased after the second injection, particularly with the blended CYD-1;3;4/ VDV-2 vaccine. In the bivalent vaccine group, immune response against serotype 3 was highest and the second injection elicited a low immune response against CYD 2 and 4. Immune responses after the first injection of CYD-TDV in the JE-primed group were in general higher than after the first injection in the other groups. All tested regimens were well tolerated without marked differences between groups. Bivalent vaccination showed no advantage in terms of immunogenicity., Clinical Trial Registration Number: NCT00740155.

Background: Dengue disease is a major public health problem across the Asia-Pacific region for which there is no licensed vaccine or treatment. We evaluated the safety and immunogenicity of Phase III lots of a candidate vaccine (CYD-TDV) in children in Malaysia., Methods: In this observer-blind, placebo-controlled, Phase III study, children aged 2-11 years were randomized (4:1) to receive CYD-TDV or placebo at 0, 6 and 12 months. Primary endpoints included assessment of reactogenicity following each dose, adverse events (AEs) and serious AEs (SAEs) reported throughout the study, and immunogenicity expressed as geometric mean titres (GMTs) and distribution of dengue virus (DENV) neutralizing antibody titres., Results: 250 participants enrolled in the study (CYD-TDV: n=199; placebo: n=51). There was a trend for reactogenicity to be higher with CYD-TDV than with placebo post-dose 1 (75.4% versus 68.6%) and post-dose 2 (71.6% versus 62.0%) and slightly lower post-dose 3 (57.9% versus 64.0%). Unsolicited AEs declined in frequency with each subsequent dose and were similar overall between groups (CYD-TDV: 53.8%; placebo: 49.0%). Most AEs were of Grade 1 intensity and were transient. SAEs were reported by 5.5% and 11.8% of participants in the CYD-TDV and placebo groups, respectively. No deaths were reported. Baseline seropositivity against each of the four DENV serotypes was similar between groups, ranging from 24.0% (DENV-4) to 36.7% (DENV-3). In the CYD-TDV group, GMTs increased post-dose 2 for all serotypes compared with baseline, ranging from 4.8 (DENV-1) to 8.1-fold (DENV-3). GMTs further increased post-dose 3 for DENV-1 and DENV-2. Compared with baseline, individual titre increases ranged from 6.1-fold (DENV-1) to 7.96-fold (DENV-3)., Conclusions: This study demonstrated a satisfactory safety profile and a balanced humoral immune response against all four DENV serotypes for CYD-TDV administered via a three-dose regimen to children in Malaysia., (Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.)

To characterize the cell mediated immunity (CMI) induced by the investigational CYD tetravalent dengue vaccine (TDV), we developed a whole-blood, intracellular cytokine staining (ICS) assay and a multiplex assay, each requiring 3 mL of blood. We assessed CMI before and 28 d after a first and third injection of CYD-TDV and one year after the third injection in a subset of 80 adolescents and adults enrolled in a phase II trial in Singapore (ClinicalTrial.gov NCT NCT00880893). CD4/IFNγ/TNFα responses specific to dengue NS3 were detected before vaccination. Vaccination induced YF-17D-NS3-specific CD8/IFNγ responses, without significant TNFα, and a CYD-specific Th1/Tc1 cellular response in all participants, which was characterized by predominant IFNγ secretion compared with TNFα, associated with low level IL-13 secretion in multiplex analysis of peripheral blood mononuclear cells (PBMC) supernatants after restimulation with each the CYD vaccine viruses. Responses were directed mainly against CYD-4 after the first vaccination, and were more balanced against all four serotypes after the third vaccination. The same qualitative profile was observed one year after the third vaccination, with approximately 2-fold lower NS3-specific responses, and 3-fold lower serotype-specific cellular responses. These findings confirm previous observations regarding both the nature and specificity of cellular responses induced by CYD-TDV, and for the first time demonstrate the persistence of cellular responses after one year. We also established the feasibility of analyzing CMI with small blood samples, allowing such analysis to be considered for pediatric trials.

Background: Roughly half the world's population live in dengue-endemic countries, but no vaccine is licensed. We investigated the efficacy of a recombinant, live, attenuated tetravalent dengue vaccine., Methods: In this observer-masked, randomised, controlled, monocentre, phase 2b, proof-of-concept trial, healthy Thai schoolchildren aged 4-11 years were randomly assigned (2:1) to receive three injections of dengue vaccine or control (rabies vaccine or placebo) at months 0, 6, and 12. Randomisation was by computer-generated permuted blocks of six and participants were assigned with an interactive response system. Participants were actively followed up until month 25. All acute febrile illnesses were investigated. Dengue viraemia was confirmed by serotype-specific RT-PCR and non-structural protein 1 ELISA. The primary objective was to assess protective efficacy against virologically confirmed, symptomatic dengue, irrespective of severity or serotype, occurring 1 month or longer after the third injection (per-protocol analysis). This trial is registered at ClinicalTrials.gov, NCT00842530., Findings: 4002 participants were assigned to vaccine (n=2669) or control (n=1333). 3673 were included in the primary analysis (2452 vaccine, 1221 control). 134 cases of virologically confirmed dengue occurred during the study. Efficacy was 30·2% (95% CI -13·4 to 56·6), and differed by serotype. Dengue vaccine was well tolerated, with no safety signals after 2 years of follow-up after the first dose., Interpretation: These data show for the first time that a safe vaccine against dengue is possible. Ongoing large-scale phase 3 studies in various epidemiological settings will provide pivotal data for the CYD dengue vaccine candidate., Funding: Sanofi Pasteur., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

This was a multicenter, blinded, Phase II study (NCT00880893) conducted in Singapore. The primary objectives were to evaluate the safety of a tetravalent dengue vaccine (TDV) comprising four recombinant, live, attenuated viruses (CYD-TDV) and the dengue virus serotype-specific antibody responses before and 28 d after each vaccination. Participants were randomized 3:1 to receive three doses of CYD-TDV or a control vaccine at 0, 6 and 12 mo. Control vaccine was placebo for the first dose (all ages) and for subsequent doses, licensed hepatitis-A for children (aged 2-11 y) or influenza vaccine for adolescents (12-17 y) and adults (18-45 y). Between April and October 2009, 317 children, 187 adolescents and 696 adults were enrolled. In all age groups, reactogenicity was higher after the first injection of CYD-TDV than after placebo control. Reactogenicity after subsequent CYD-TDV doses was no higher than after the first dose, and tended to be lower or similar to that seen after active control vaccination. Seropositivity rates and geometric mean neutralizing antibody titers (GMTs; 1/dil) against all four dengue virus serotypes increased in all age groups after each of the three CYD-TDV doses. Post-dose 3, 66.5% of all participants were seropositive to all four serotypes, and 87.2% were seropositive to ≥ 3 serotypes; GMTs for all participants ranged from 43.0 against dengue virus serotype 1 to 100 against dengue virus serotype 4. GMTs were higher in children than in adolescents. These results support the continued development of CYD-TDV for the prevention of dengue disease.