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VLA1553 is a live-attenuated vaccine candidate for active immunisation and prevention of disease caused by chikungunya virus. We report safety and immunogenicity data up to day 180 after vaccination with VLA1553. This double-blind, multicentre, randomised, phase 3 trial was done in 43 professional vaccine trial sites in the USA. Eligible participants were healthy volunteers aged 18 years and older. Patients were excluded if they had history of chikungunya virus infection or immune-mediated or chronic arthritis or arthralgia, known or suspected defect of the immune system, any inactivated vaccine received within 2 weeks before vaccination with VLA1553, or any live vaccine received within 4 weeks before vaccination with VLA1553. Participants were randomised (3:1) to receive VLA1553 or placebo. The primary endpoint was the proportion of baseline negative participants with a seroprotective chikungunya virus antibody level defined as 50% plaque reduction in a micro plaque reduction neutralisation test (μPRNT) with a μPRNT50 titre of at least 150, 28 days after vaccination. The safety analysis included all individuals who received vaccination. Immunogenicity analyses were done in a subset of participants at 12 pre-selected study sites. These participants were required to have no major protocol deviations to be included in the per-protocol population for immunogenicity analyses. This trial is registered at ClinicalTrials.gov, NCT04546724. Between Sept 17, 2020 and April 10, 2021, 6100 people were screened for eligibility. 1972 people were excluded and 4128 participants were enrolled and randomised (3093 to VLA1553 and 1035 to placebo). 358 participants in the VLA1553 group and 133 participants in the placebo group discontinued before trial end. The per-protocol population for immunogenicity analysis comprised 362 participants (266 in the VLA1553 group and 96 in the placebo group). After a single vaccination, VLA1553 induced seroprotective chikungunya virus neutralising antibody levels in 263 (98·9%) of 266 participants in the VLA1553 group (95% CI 96·7–99·8; p<0·0001) 28 days post-vaccination, independent of age. VLA1553 was generally safe with an adverse event profile similar to other licensed vaccines and equally well tolerated in younger and older adults. Serious adverse events were reported in 46 (1·5%) of 3082 participants exposed to VLA1553 and eight (0·8%) of 1033 participants in the placebo arm. Only two serious adverse events were considered related to VLA1553 treatment (one mild myalgia and one syndrome of inappropriate antidiuretic hormone secretion). Both participants recovered fully. The strong immune response and the generation of seroprotective titres in almost all vaccinated participants suggests that VLA1553 is an excellent candidate for the prevention of disease caused by chikungunya virus. Valneva, Coalition for Epidemic Preparedness Innovation, and EU Horizon 2020.

Chikungunya is an emerging arthropod-borne disease that has spread from tropical endemic areas to more temperate climates of the USA and Europe. However, no specific treatment or preventive measure is yet available. We aimed to investigate the immunogenicity and safety of a live recombinant measles-virus-based chikungunya vaccine. We did a randomised, double-blind, placebo-controlled, active-comparator, phase 1, dose-escalation study at one centre in Vienna, Austria. Healthy men and women aged 18–45 years with no comorbidities were randomly assigned, by computer-generated block randomisation (block size of 14), to receive either one of three escalating doses of the measles-virus-based candidate vaccine (low dose [1·5 × 104 median tissue culture infection doses (TCID50) per 0·05 mL], medium dose [7·5 × 104 TCID50 per 0·25 mL], or high dose [3·0 × 105 TCID50 per 1·0 mL]), or the active comparator—Priorix. Participants were additionally block-randomised to receive a booster injection on either day 28 or day 90 after the first vaccination. Participants and study investigators were masked to group allocation. The primary endpoint was the presence of neutralising anti-chikungunya antibodies on day 28, as assessed by 50% plaque reduction neutralisation test. Analysis was by intention to treat and per protocol. This trial is registered with EudraCT, number 2013-001084-23. Between Nov 22, 2013, and Feb 25, 2014, we randomly assigned 42 participants to receive the low dose (n=12), the medium dose (n=12), or the high dose (n=12) of the measles-virus-based candidate vaccine, or Priorix (n=6), of whom 36 participants (86%; n=9, n=12, n=10, n=5, respectively) were included in the per-protocol population. The candidate vaccine raised neutralising antibodies in all dose cohorts after one immunisation, with seroconversion rates of 44% (n=4) in the low-dose group, 92% (n=11) in the medium-dose group, and 90% (n=10) in the high-dose group. The immunogenicity of the candidate vaccine was not affected by pre-existing anti-measles immunity. The second vaccination resulted in a 100% seroconversion for all participants in the candidate vaccine groups. The candidate vaccine had an overall good safety profile, and the rate of adverse events increased with vaccine dose and volume. No vaccination-related serious adverse events were recorded. The live recombinant measles-virus-based chikungunya vaccine had good immunogenicity, even in the presence of anti-vector immunity, was safe, and had a generally acceptable tolerability profile. This vaccine is the first promising measles-virus-based candidate vaccine for use in human beings. Themis Bioscience GmBH.

Chikungunya virus infection can lead to long-term debilitating symptoms. A precursor phase 3 clinical study showed high seroprotection (defined as a 50% plaque reduction of chikungunya virus-specific neutralising antibodies on a micro plaque reduction neutralisation test [μPRNT] titre of ≥150 in baseline seronegative participants) up to 6 months after a single vaccination of the chikungunya virus vaccine VLA1553 (Valneva Austria, Vienna, Austria) and a good safety profile. Here we report antibody persistence and safety up to 2 years. In this single-arm, multicentre, phase 3b study, we recruited participants from the precursor phase 3 trial from professional vaccine trial sites in the USA. Participants (aged ≥18 years) were eligible if they had completed the previous study and received VLA1553. Chikungunya virus-specific neutralising antibodies were evaluated at 28 days, 6 months, and 1 year and 2 years after vaccination. The primary outcome was the proportion of seroprotected participants (ie, μPRNT50 titre of ≥150) at 1 and 2 years, assessed in all eligible participants who had at least one post-vaccination immunogenicity sample available, overall and by age group at the time of vaccination (18–64 years and ≥65 years). Adverse events of special interest at the time of transition from the previous study to the current study (ie, at 6 months) and serious adverse events during the current study were recorded (ie, between 6 months and 2 years). All analyses were descriptive. This study is registered with ClinicalTrials.gov, NCT04838444, and immunogenicity follow-up is ongoing. In the precursor study, participants were screened between Sept 17, 2020, and April 10, 2021; data cutoff for this analysis was March 31, 2023. Of 2724 participants in the precursor study who received one dose of VLA1553, 363 participants were analysed in this study (310 [85%] aged 18–64 years and 53 [15%] aged ≥65 years at enrolment in the precursor study; mean age 47·7 years [SD 14·2], 207 [57%] of 363 participants were female, 156 [43%] were male, 280 [77%] were White, and 314 [87%] were not Hispanic or Latino). Strong seroprotection was observed at 1 year (98·9% [356 of 360 assessable participants; 97·2–99·7]) and 2 years (96·8% [306 of 316; 94·3–98·5]) after vaccination, and was very similar between those aged 18–64 years (at 1 year: 98·7% [303 of 307; 96·7–99·6]; at 2 years: 96·6% [256 of 265; 93·7–98·4]) and those aged 65 years and older (at 1 year: 100% [53 of 53; 93·3–100]; at 2 years: 98·0% [50 of 51; 89·6–100]) at each timepoint. No adverse events of special interest were ongoing at the time of transition. Ten serious adverse events occurred in nine (2%) participants between the 6-month and 2-year timepoints, including one death (due to drug overdose) that was determined to not be related to VLA1553. After a single VLA1553 vaccination, chikungunya virus-neutralising antibodies above the threshold considered to be protective persisted up to 2 years and there were no long-term serious adverse events related to vaccination. VLA1553 is an efficient and safe intervention that offers high seroprotection against chikungunya virus infection, a virus likely to spread globally with an urgent demand for long-lasting prophylaxis. Valneva Austria, Coalition for Epidemic Preparedness Innovation, and EU Horizon 2020.

Chikungunya outbreaks have been reported in Brazil since 2014. Adolescents are a sensitive population who would benefit from a prophylactic vaccine. This study assessed the immunogenicity and safety of the vaccine VLA1553 in adolescents in Brazil. With an overall trial duration of 12 months, we now report data on safety and immunogenicity over a period of 28 days after vaccination. In this double-blind, randomised, placebo-controlled phase 3 trial, adolescents aged 12 to <18 years were recruited. The trial was performed at ten trial sites across Brazil. Eligible participants were generally healthy. The main exclusion criteria comprised immune-mediated or chronic arthritis or arthralgia, a known or suspected defect of the immune system, or any live vaccine received within the 4 weeks before trial vaccination. Randomisation was stratified by baseline serostatus in a 2:1 ratio to receive VLA1553 (at a dose of 1 × 104 TCID50 per 0·5 mL [ie, 50% tissue culture infectious dose]) or placebo. VLA1553 or placebo was administered intramuscularly as a single-dose immunisation on day 1. The primary endpoint was the proportion of baseline seronegative participants with chikungunya virus neutralising antibody levels of 150 or more in μPRNT50 (a micro plaque reduction neutralisation test), which was considered a surrogate of protection. The safety analysis included all participants receiving a trial vaccination. Immunogenicity analyses were performed in a subset. The trial is registered with ClinicalTrials.gov, NCT04650399. Between Feb 14, 2022, and March 14, 2023, 754 participants received a trial vaccination (502 received VLA1553 and 252 received placebo) with a per-protocol population of 351 participants for immunogenicity analyses (303 in the VLA1553 group and 48 in the placebo group). In participants who were seronegative at baseline, VLA1553 induced seroprotective chikungunya virus neutralising antibody levels in 247 of 250 (98·8%, 95% CI 96·5–99·8) participants 28 days after vaccination. In seropositive participants, the baseline seroprotection rate of 96·2% increased to 100% after vaccination with VLA1553. Most (365 [93%] of 393) adverse events were of mild or moderate intensity, VLA1553 was generally well tolerated. When compared with placebo, participants exposed to VLA1553 had a significantly higher frequency of related adverse events (351 [69·9%] of 502 vs 121 [48·0%] of 252; p<0·0001), mostly headache, myalgia, fatigue, and fever. Among four reported serious adverse events (three in the VLA1553 group and one in the placebo group), one was classified as possibly related to VLA1553: a high-grade fever. Among 20 adverse events of special interest (ie, symptoms suggesting chikungunya-like disease), 16 were classified as related to trial vaccination (15 in the VLA1553 group and one in the placebo group), with severe symptoms reported in four participants (fever, headache, or arthralgia). 17 adverse events of special interest resolved within 1 week. Among 85 participants with arthralgia (68 in the VLA1553 group and 17 in the placebo group), eight adolescents had short-lived (range 1–5 days), mostly mild recurring episodes (seven in the VLA1553 group and one in the placebo group). The median duration of arthralgia was 1 day (range 1–5 days). The frequency of injection site adverse events for VLA1553 was higher than in the placebo group (161 [32%] vs 62 [25%]), but rarely severe (two [<1%] in the VLA1553 group and one [<1%] in the placebo group). After administration of VLA1553, there was a significantly lower frequency of solicited adverse events in participants who were seropositive at baseline compared with those who were seronegative (53% vs 74%; p<0·0001) including headache, fatigue, fever, and arthralgia. VLA1553 was generally safe and induced seroprotective titres in almost all vaccinated adolescents with favourable safety data in adolescents who were seropositive at baseline. The data support the use of VLA1553 for the prevention of disease caused by the chikungunya virus among adolescents and in endemic areas. Coalition for Epidemic Preparedness Innovation and EU Horizon 2020. For the Portuguese translation of the abstract see Supplementary Materials section.

Chikungunya disease is a growing global public health concern. Vimkunya (previously chikungunya virus virus-like particle vaccine, previously PXVX0317) is a single-dose, pre-filled syringe for intramuscular injection. Here, we report safety, tolerability, and immunogenicity data for Vimkunya versus placebo in healthy adolescents and adults aged 12–64 years, and evaluate lot-to-lot consistency. This pivotal phase 3, randomised, double-blind, placebo-controlled, parallel-group trial was done at 47 clinical trial sites in the USA. Eligible participants were healthy adolescents and adults aged 12–64 years. Participants were divided into three age strata (12–17 years, 18–45 years, and 46–64 years) within each site and randomly assigned (2:2:2:1) to receive one of three consecutively manufactured lots of Vimkunya or placebo (same excipient composition without chikungunya virus virus-like particle or aluminium hydroxide components) on study day 1. Neither participants, nor clinical site personnel, nor the funder knew participants' individual treatment assignments until all participants completed their involvement in the trial and the database was cleaned and locked. Participants attended a screening visit, followed by a day 1 visit that included random assignment, blood sample collection, and administration of a single dose of Vimkunya or placebo by intramuscular injection in the deltoid muscle. The coprimary endpoints were: the difference in chikungunya virus serum neutralising antibody seroreponse rate (vaccine minus placebo) at day 22; chikungunya virus serum neutralising antibody geometric mean titre (GMT) at day 22 for vaccine and placebo; and chikungunya virus serum neutralising GMT ratio at day 22 between all three pairs of vaccine lots (A:B, B:C, and A:C) in adults aged 18–45 years. The trial is registered with ClinicalTrials.gov, NCT05072080 and EudraCT, 2023-001124-42. Between Sept 29, 2021, and Sept 23, 2022, 4215 participants were screened, of whom 3258 were eligible and enrolled (1667 [51·2%] female and 1591 [48·8%] male), and 3254 (99·9%) received either Vimkunya (n=2790) or placebo (n=464). The immunogenicity evaluable population included 2983 participants, of whom 2559 received Vimkunya and 424 received placebo. At day 22, 2503 (97·8%) of 2559 participants in the Vimkunya group had a seroresponse, compared with five (1·2%) of 424 participants in the placebo group for the immunogenicity evaluable population. The seroreponse rate difference was 96·6% (95% CI 95·0–97·5; p<0·0001). In the immunogenicity evaluable population, chikungunya virus serum neutralising antibody GMT at day 22 for the vaccine group was 1618 and for the placebo group was 7·9 (p<0·0001). At day 22, the serum neutralising GMT ratios for the pairs of lots (A:B, B:C, and A:C) were 0·98 (95% CI 0·85–1·14), 0·97 (0·84–1·12), and 0·95 (0·82–1·10), respectively. Vimkunya had a favourable safety profile; most adverse events were self-limiting and grade 1 or 2 in severity. The most common adverse events were injection site pain (656 [23·7%] of 2764 participants in the vaccine group), fatigue (551 [19·9%] of 2764), headache (498 [18·0%] of 2765), and myalgia (486 [17·6%] of 2764). Vimkunya induces a rapid and robust immune response. These findings support the potential for this vaccine to protect individuals aged 12–64 years from disease caused by chikungunya virus. Emergent BioSolutions and Bavarian Nordic.

Targeted indoor residual spraying focuses insecticide applications on common resting surfaces of mosquitoes (an arboviral disease vector) in houses, such as exposed lower sections of walls and under furniture. We conducted a two-group, parallel, unblinded, cluster-randomized trial in Merida, Mexico, to quantify the efficacy of targeted indoor residual spraying for preventing aedes-borne diseases (chikungunya, dengue, or Zika). Children 2 to 15 years of age were enrolled from households in 50 clusters of five-by-five city blocks. Households in 25 clusters received an annual application of targeted indoor residual spraying (intervention) before each season of aedes-borne disease (July through December). All clusters received routine Ministry of Health vector control. The primary end point was laboratory-confirmed, symptomatic aedes-borne disease. Community effects were assessed with the use of geolocated national surveillance data. A total of 4461 children were monitored for up to three seasons (2021, 2022, and 2023). The indoor density of mosquitoes was 59% (95% confidence interval [CI], 51 to 65) lower with the intervention than with control. A total of 422 cases of aedes-borne disease were confirmed, primarily dengue in 2023. In the per-protocol analysis of cluster centers, 91 cases occurred among 1038 participants in the intervention group and 89 cases among 1037 participants in the control group (efficacy, -12.8%; 95% CI, -60.7 to 23.0). In an intention-to-treat analysis of entire clusters, 198 cases occurred among 2239 participants in the intervention group and 199 cases among 2222 participants in the control group (efficacy, 3.9%; 95% CI, -28.1 to 26.7). Adjustment of analyses for mobility or demographic characteristics did not change results. On the basis of 150 cases in the intervention clusters and 202 in the control clusters that were geolocated, the estimated community effect of the intervention was 24.0% (95% CI, 6.0 to 38.6). Two cases of multisymptom adverse events (e.g., nausea, watery eyes, diarrhea, and vomiting) were associated with the intervention. Despite lower entomologic indexes with targeted indoor residual spraying than with routine vector control, the cumulative incidence of aedes-borne diseases was not significantly lower with targeted indoor residual spraying. (Funded by the National Institutes of Health and the Innovative Vector Control Consortium; ClinicalTrials.gov number, NCT04343521.).

Adults older than 65 years are at increased risk for atypical presentations of chikungunya disease, as well as for severe outcomes including death. In this phase 3, randomised, double-blind, placebo-controlled, parallel-group trial, adults aged 65 years and older received a single intramuscular dose of Vimkunya (previously chikungunya virus virus-like particle vaccine) or placebo at ten sites in the USA. Participants, clinical site personnel, and the sponsor were masked to individual treatment assignments until all participants had completed their involvement in the trial and the database was cleaned and locked. Baseline and postvaccination chikungunya virus serum neutralising antibody (SNA) titres (NT80) were assessed at selected timepoints. Safety was assessed up to 183 days after dose administration in all participants from the exposed population who provided safety assessment data. This trial is registered with ClinicalTrials.gov, NCT05349617, and is completed. Between May 12 and Dec 2, 2022, 413 participants were recruited and randomly assigned (1:1) to receive the Vimkunya vaccine (n=206) or placebo (n=207). The coprimary endpoints of immunologic superiority of chikungunya virus SNA titres compared with placebo and geometric mean titre at day 22 were met. Vimkunya induced a protective seroresponse (SNA NT80≥100, considered the presumptive seroprotective antibody response) in 149 (82%) of 181 participants (95% CI 76·1–87·2) at day 15, in 165 (87%) of 189 participants (81·8–91·3) at day 22, and in 139 (76%) of 184 participants (68·9–81·2) at day 183. Although there was a slightly higher early immune response in the 65–74 years age group at day 15 compared with the 75 years and older age group, the seroresponse rates at day 22 and day 183 were similar. There were no notable differences in adverse event rates between groups, and most adverse events were grade 1 or 2 in severity and of short duration. No vaccine-related serious adverse events or deaths occurred. We provide robust data from adults aged 65 years and older showing that Vimkunya is well tolerated and can provide a high rate of protection within 2 weeks postvaccination and during 6 months of follow-up. Emergent BioSolutions and Bavarian Nordic.

Aedes mosquito-borne viruses (ABVs) place a substantial strain on public health resources in the Americas. Vector control of Aedes mosquitoes is an important public health strategy to decrease or prevent spread of ABVs. The ongoing Targeted Indoor Residual Spraying (TIRS) trial is an NIH-sponsored clinical trial to study the efficacy of a novel, proactive vector control technique to prevent dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) infections in the endemic city of Merida, Yucatan, Mexico. The primary outcome of the trial is laboratory-confirmed ABV infections in neighborhood clusters. Despite the difficulties caused by the COVID-19 pandemic, by early 2021 the TIRS trial completed enrollment of 4,792 children aged 2–15 years in 50 neighborhood clusters which were allocated to control or intervention arms via a covariate-constrained randomization algorithm. Here, we describe the makeup and ABV seroprevalence of participants and mosquito population characteristics in both arms before TIRS administration. Baseline surveys showed similar distribution of age, sex, and socio-economic factors between the arms. Serum samples from 1,399 children were tested by commercially available ELISAs for presence of anti-ABV antibodies. We found that 45.1% of children were seropositive for one or more flaviviruses and 24.0% were seropositive for CHIKV. Of the flavivirus-positive participants, most were positive for ZIKV-neutralizing antibodies by focus reduction neutralization testing which indicated a higher proportion of participants with previous ZIKV than DENV infections within the cohort. Both study arms had statistically similar seroprevalence for all viruses tested, similar socio-demographic compositions, similar levels of Ae . aegypti infestation, and similar observed mosquito susceptibility to insecticides. These findings describe a population with a high rate of previous exposure to ZIKV and lower titers of neutralizing antibodies against DENV serotypes, suggesting susceptibility to future outbreaks of flaviviruses is possible, but proactive vector control may mitigate these risks.

Chikungunya virus (CHIKV) is an alphavirus that has emerged as a global health burden. There are 3 CHIKV genotypes: Asian, West African, and Eastern/Central/South African. No licensed CHIKV vaccine is available, and whether the antibody response elicited by one genotype can neutralize heterologous genotypes is unclear. We assessed neutralizing antibody (NAb) responses of volunteers in a phase 1 study of a CHIKV vaccine against 9 viral strains representing all 3 genotypes. Minimal differences in vaccine-elicited NAb responses were observed among genotypes, suggesting that vaccination with a single CHIKV strain can elicit cross-protective NAbs against all 3 genotypes.

Abstract Background The global spread of the chikungunya virus (CHIKV) increases the exposure risk for individuals travelling to or living in endemic areas. This Phase 3 study was designed to demonstrate manufacturing consistency between three lots of the single shot live-attenuated CHIKV vaccine VLA1553, and to confirm the promising immunogenicity and safety data obtained in previous trials. Methods This randomized, double-blinded, lot-to-lot consistency, Phase 3 study, assessed immunogenicity and safety of VLA1553 in 408 healthy adults (18–45 years) in 12 sites across the USA. The primary endpoint was a comparison of the geometric mean titre (GMT) ratios of CHIKV-specific neutralizing antibodies between three VLA1553 lots at 28 days post-vaccination. Secondary endpoints included immunogenicity and safety over 6 months post-vaccination. Results GMTs were comparable between the lots meeting the acceptance criteria for equivalence. The average GMT (measured by 50% CHIKV micro plaque neutralization test; μPRNT50) peaked with 2643 at 28 days post-vaccination and decreased to 709 at 6 months post-vaccination. An excellent seroresponse rate (defined as μPRNT50 titre ≥ 150 considered protective) was achieved in 97.8% of participants at 28 days post-vaccination and still persisted in 96% at 6 months after vaccination. Upon VLA1553 immunization, 72.5% of participants experienced adverse events (AEs), without significant differences between lots (related solicited systemic AE: 53.9% of participants; related solicited local AE: 19.4%). Overall, AEs were mostly mild or moderate and resolved without sequela, usually within 3 days. With 3.9% of participants experiencing severe AEs, 2.7% were classified as related, whereas none of the six reported serious adverse events was related to the administration of VLA1553. Conclusions All three lots of VLA1553 recapitulated the safety and immunogenicity profiles of a preceding Phase 3 study, fulfilling pre-defined consistency requirements. These results highlight the manufacturability of VLA1553, a promising vaccine for the prevention of CHIKV disease for those living in or travelling to endemic areas.