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
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 three 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 five years after the last injection.
Results
In those aged ≥9 years and baseline seropositive, CYD-TDV protected against hospitalized and severe VCD over six years compared to placebo (HR [95% confidence interval] Multiple Imputation from Month 0 method, 0.19 [0.12–0.30] and 0.15 [0.06–0.39]; 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 six-year follow-up in participants who were seropositive and ≥9 years old. Protection was also observed in seropositive 6–8 year olds.
This study shows that the immune response elicited by a Japanese encephalitis chimeric virus vaccine (JE-CV) booster in JE-CV–primed children in the Philippines induces long-lasting protection, and further supports the benefit of a booster irrespective of when primary vaccination was administered.
Background
The immune profile of dengue-experienced individuals is a determinant of dengue reinfection severity risk. Individuals with a single prior dengue infection (monotypic) are at highest risk for severe disease, while individuals with ≥ 2 prior dengue infections (multitypic) are at lower risk. The tetravalent dengue vaccine (CYD-TDV) has shown efficacy in the prevention of dengue in individuals with prior dengue infection. We estimated efficacy in individuals with monotypic or multitypic immune profiles.
Methods
Participants enrolled in the immunogenicity subsets of 2 randomized placebo-controlled phase 3 studies (CYD14, NCT01373281; CYD15, NCT01374516) were classified as either monotypic or multitypic, based on measured baseline dengue plaque reduction neutralization test. Vaccine efficacy (VE) against symptomatic virologically confirmed dengue (VCD) was assessed over 25 months and against VCD hospitalization over 6 years.
Results
Of 3927 participants in the immunogenicity subsets, 496 and 257 in the CYD-TDV and placebo groups, respectively, were classified as monotypic immune, and 1227 and 612, respectively, as multitypic immune. VE against symptomatic VCD was 77.4% (95% CI, 56.4%–88.2%) for monotypic and 89.2% (95% CI, 71.5%–95.9%) for multitypic profiles, with corresponding absolute risk reductions (ARRs) of 4.48% (95% CI, 2.32%–6.65%) for monotypics and 1.67% (95% CI, .89%–2.46%) for multitypics. VE against hospitalized VCD was 75.3% (95% CI, 42.7%–90.2%) in monotypics and 81.2% (95% CI, 21.7%–96.8%) in multitypics, with ARRs of 0.95% (95% CI, .37%–1.53%) for monotypics and 0.18% (95% CI, .02%–.34%) for multitypics.
Conclusions
CYD-TDV benefits individuals with monotypic and multitypic immune profiles. Larger public health benefit is expected to derive from the protection of individuals with a monotypic immune profile.
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