Accuracy and efficacy of pre-dengue vaccination screening for previous dengue infection with a new dengue rapid diagnostic test: a retrospective analysis of phase 3 efficacy trials.

BACKGROUND: A dengue pre-vaccination test that is convenient, highly specific, and highly sensitive is still needed. The OnSite Dengue IgG rapid diagnostic test (RDT) is a new rapid diagnostic test specifically designed for pre-vaccination screening. We aimed to retrospectively assess the efficacy of a tetravalent dengue vaccine (CYD-TDV) in participants determined to be dengue seropositive by the OnSite IgG RDT and to evaluate assay performances. METHODS: This was a complementary study using pre-vaccination samples from two CYD-TDV efficacy trials done in five countries in the Asia-Pacific region (NCT01373281) and five countries in Latin America (NCT01374516). Baseline dengue serostatus was determined by the OnSite IgG RDT on samples from the immunogenicity subsets of the two trials. In participants who were test positive, we calculated CYD-TDV vaccine efficacy against symptomatic virologically confirmed dengue (VCD) over 25 months, and against hospitalisation with VCD over 72 months of follow-up after the first vaccination. We used a reference algorithm to determine the reference dengue serostatus for each sample, and sensitivity and specificity of the OnSite IgG RDT were calculated. Analyses were done on the whole population (aged 2-16 years), and on those aged 6 years or older and those aged 9 years or older. FINDINGS: Of 3983 participants in the immunogenicity subsets of the efficacy trials CYD14 and CYD15, 3962 had complete dengue reference test results enabling baseline serostatus classification and 3833 had sufficient serum samples remaining for evaluation with the OnSite IgG RDT. Of the samples tested, 2486 (64·9%) of 3833 were OnSite IgG RDT-positive. In participants aged 2-16 years who were OnSite IgG RDT-positive, vaccine efficacy was 84·1% (95% CI 71·6-91·1) against symptomatic VCD, and 69·2% (38·8-84·5) against hospitalisation with VCD, with similar findings in those aged 6 years or older and those aged 9 years or older. The OnSite IgG RDT showed very high sensitivity (91·1%, 89·9-92·1) and high specificity (92·8%, 91·2-94·2) in participants aged 2-16 years, with significantly higher specificity in those aged 9 years or older (96·6%, 94·9-97·8). INTERPRETATION: The OnSite IgG RDT should provide a valuable tool for screening for previous dengue infection at the point of vaccination. In individuals who were OnSite IgG RDT-positive, the vaccine efficacy of CYD-TDV was high across all three age groups. FUNDING: Sanofi Pasteur.

A New Electrochemiluminescence-Based Multiplex Assay for the Assessment of Human Antibody Responses to Bordetella pertussis Vaccines.

INTRODUCTION: Commercially available enzyme-linked immunosorbent assay (ELISA) kits designed for pertussis diagnostic purposes are frequently used to assess antibody responses to pertussis vaccines in clinical trials, but have limited accuracy and are not calibrated against international standards. We developed a new electrochemiluminescence (ECL)-based multiplexed assay and compared its performance to two commercial Bordetella pertussis ELISA kits and to historical in-house ELISAs. METHODS: The ECL assay quantifies serum concentrations of antibodies against four B. pertussis antigens: pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (PRN), and fimbrial agglutinogen (FIM). The assay was validated for precision, accuracy, dilutability, lower limit of quantification, and specificity. Sera from a clinical trial (CTRI/2016/11/007434) were used to compare the ECL assay to two commercial ELISA kits available from GenWay BioTech and Demeditec Diagnostics for accuracy, linearity, specificity, and concordance to both internal (WWO-2-043) and international (NIBSC 06/140) references. Sera from four clinical trials (NCT02587520, NCT00255047, NCT00347958, NCT01346293) were used to compare the concordance to clinical ELISAs. Informed consent was ensured prior to using any sera. RESULTS: Precision, accuracy, dilutability, lower limit of quantification, and specificity were demonstrated for the ECL assay. Concordance between the ECL assay and established clinical ELISAs was met for antibody responses to PT, FIM, and PRN, but not for FHA. The ECL assay demonstrated higher accuracy and linearity than the ELISA kits. While concordance between the ECL and commercial kits was low, the ECL assay better distinguished between pre- and post-vaccination clinical samples. CONCLUSION: The new ECL assay was validated for the quantitative evaluation of anti-PT, anti-FHA, anti-FIM, and anti-PRN IgG antibodies in samples from clinical trials, and demonstrated equivalent or better performance than two commercially available ELISA kits.

Accuracy and efficacy of pre-dengue vaccination screening for previous dengue infection with five commercially available immunoassays: a retrospective analysis of phase 3 efficacy trials.

BACKGROUND: The tetravalent dengue vaccine (CYD-TDV) has been shown to provide protection against dengue disease over 5-year follow-up in participants with previous dengue infection, but increased the risk of dengue hospitalisation and severe dengue during long-term follow-up in those without previous dengue infection. WHO recommended pre-vaccination screening to identify those with previous dengue infection (ie, dengue seropositive) who would benefit from vaccination. We re-evaluated CYD-TDV efficacy in those identified as dengue seropositive using five commercially available immunoassays, and assessed immunoassay performance. METHODS: We included participants in the immunogenicity subsets of the phase 3 CYD14 (NCT01373281) and CYD15 (NCT01374516) CYD-TDV efficacy trials, which enrolled children aged 2-16 years in 2011-12 in five countries in the Asia-Pacific region (CYD14) and five Latin American countries (CYD15). Participants assessed had received at least one injection of study drug (CYD-TDV or placebo) and had baseline samples available. We tested baseline samples by IgG-based immunoassays to classify baseline dengue serostatus, using two ELISAs (EUROIMMUN and Panbio) and three rapid diagnostic tests (RDTs; TELL ME FAST, SD BIOLINE, and OnSite). Vaccine efficacy in preventing symptomatic, hospitalised, and severe virologically confirmed dengue was determined for participants who tested positive by each immunoassay. The specificity and sensitivity of each immunoassay was determined as percentage negative and positive agreement compared with the reference algorithm, which used dengue plaque reduction neutralisation test with 50% and 90% cutoffs and non-structural protein 1 IgG ELISA results to assign baseline serostatus. FINDINGS: Samples were available for 3967 participants, 2735 (69·0%) of whom were classified as seropositive by the reference algorithm. Vaccine efficacy against symptomatic virologically confirmed dengue in immunoassay-positive participants was high across all five immunoassays (EUROIMMUN ELISA 88·2% [95% CI 77·3 to 93·9], Panbio ELISA 87·6% [76·7 to 93·4], TELL ME FAST RDT 88·8% [67·0 to 96·2], SD BIOLINE RDT 82·8% [66·9 to 91·1], and OnSite RDT 89·7% [64·6 to 97·0]), as was vaccine efficacy against hospitalised virologically confirmed dengue (EUROIMMUN-ELISA 72·8% [38·9 to 87·9], Panbio ELISA 77·5% [52·8 to 89·3], TELL ME FAST RDT 92·4% [37·8 to 99·1], SD BIOLINE RDT 87·2% [54·5 to 96·4], and OnSite RDT 73·7% [-5·1 to 93·4]) and severe virologically confirmed dengue (EUROIMMUN ELISA 86·9% [-16·8 to 98·5], Panbio ELISA 91·3% [27·6 to 99·0], TELL ME FAST RDT 100·0% [not estimable to 100·0%], SD BIOLINE RDT 89·4% [9·6 to 98·8], and OnSite RDT 73·4% [-193·7 to 97·6]). The immunoassays exhibited high specificity (≥98·8% for all immunoassays apart from SD BIOLINE RDT) but variable sensitivities, with higher sensitivities observed for the ELISAs (EUROIMMUN 89·2% [87·9 to 90·3] and Panbio 92·5 [91·4 to 93·5]) than the RDTs (TELL ME FAST 52·5% [50·6 to 54·4], SD BIOLINE 71·1% [69·3 to 72·8], and OnSite 47·6% [45·7 to 49·5]). INTERPRETATION: Our findings suggest that these immunoassays could be used for pre-vaccination screening for CYD-TDV as tools to assist risk stratification until more sensitive and convenient tests become available. FUNDING: Sanofi Pasteur.

Preparation and qualification of internal rabies reference standards for use in the rabies rapid fluorescent focus inhibition test.

The World Health Organization (WHO) international standard rabies immune globulins (SRIGs) allow the standardisation of the cell-based rapid fluorescent-focus inhibition test (RFFIT) for rabies virus neutralising antibody measurement. SRIG stocks have been depleted. We describe the preparation and qualification of two internal rabies reference standards (IRRSs), calibrated against WHO SRIGs. Candidate IRRSs IMORAB2, from human rabies immunoglobulin; and GCIRAB1, from pooled serum samples from healthy adults immunised with licensed rabies vaccine, were generated. IRRSs were qualified for use in RFFIT based on pre-determined acceptance criteria. Unitage (IU/mL) was assigned using WHO-1 and WHO-2 SRIGs as calibrators. Geometric mean concentrations (GMCs) (% geometric coefficient of variation), calibrated against WHO-1 and WHO-2 SRIGs, were: 1.8 IU/mL (18.7%) and 1.5 IU/mL (17.8%) for IMORAB2; and 2.9 IU/mL (17.5%) and 2.5 IU/mL (16.7%), respectively, for GCIRAB1. We demonstrated IRRS specificity in competition studies using homologous (inactivated Pitman Moore rabies virus) and heterologous (inactivated vesicular stomatitis virus) antigens and acceptable accuracy/linearity of WHO SRIGs using IRRSs as calibrators. Concordance between IRRS and the WHO-1 SRIG was demonstrated using (non-)clinical human serum samples. The candidate reference standards are suitable for use as IRRS in the in-house rabies RFFIT. Funding:Sanofi Pasteur.

Evaluation of dengue serological tests available in Puerto Rico for identification of prior dengue infection for prevaccination screening.

We assessed a dengue IgG rapid diagnostic test (RDT) and IgG enzyme-linked immunosorbent assay (ELISA) to determine their suitability for dengue prevaccination screening. Each exhibited ≥99% specificity. The RDT demonstrated no Zika cross-reactivity, while the ELISA displayed greater sensitivity. Both could safely guide vaccination in Puerto Rico pending availability of improved serotests.