Safety and immunogenicity of the Euvichol-S oral cholera vaccine for prevention of Vibrio cholerae O1 infection in Nepal: an observer-blind, active-controlled, randomised, non-inferiority, phase 3 trial

Prognostication of zooplankton-driven cholera pathoepidemiological Dynamics: Novel Bayesian-regularized deep NARX neuroarchitecture

BACKGROUND

Cholera outbreaks pose significant health concerns, particularly through freshwater contamination through zooplankton serving as reservoirs for Vibrio Cholerae. Understanding these complex interactions within the aquatic ecosystem through mathematical modeling regimes may help us predict and prevent the spread of Cholera disease spread in affected regions.

METHOD

In this study, an innovative Bayesian regularized deep nonlinear autoregressive exogenous (BRDNARX) neural networks are employed to model the intricate dynamics of Zooplankton-Driven Cholera Disease Transmission (ZDCDT) system. The cholera epidemic propagation through freshwater contamination is uncovered with analysis on densities of phytoplankton, vibrio cholerae carrying zooplankton, human population vector and microbial pathogen vector populous in the marine biosphere. Synthetic data for the ZDCDT is presented for diverse simulations using a modified Adams-Bashforth-Moulton predictor corrector numerical scheme. Subsequently, these temporal data sequences are preprocessed for the novel BRDNARX computing paradigm with an exhaustive assessment on mean square error iterative convergence plots, error histogram charts, regression index reports, input-error crosscorrelation charts, error autocorrelation charts, and time-series response dynamics.

RESULTS AND CONCLUSIONS

Comparative absolute error analysis with reference numerical solution adheres to diminutive disparities of range 10-3 to 10-9. Finally, BRDNARX neurostructures are reconfigured for predictive analysis of ZDCDT system in terms of single and multi-step ahead predictors with mean square error outcomes that range from 10-9 to 10-11. This establishes the efficacy of BRDNARX in correctly adhering to the intricacies of the zooplankton-driven cholera pathoepidemiological dynamics with precise forward prognostication.

A double-blind, randomised phase III clinical trial to evaluate safety, immunogenicity, non-inferiority & lot to lot consistency of single component oral cholera vaccine BBV131 (Hillchol®) in comparison to Shanchol™

BACKGROUND

Cholera is a vaccine-preventable disease that has faced a surge in outbreaks and a shortage of vaccines. The new generation oral cholera vaccine (OCV) BBV131, featuring a simplified single stable O1 Hikojima strain, aims to enhance production efficiency and affordability. This study evaluates BBV131's immune profile, safety, and non-inferiority compared to Shanchol™ in healthy adults and children. Adding BBV131 to the vaccine stockpile could improve supply, simplify logistics, and ease administration efforts.

METHODS

In this randomised, modified, double-blind, multi-centre, phase III trial, 1800 participants were recruited across 10 clinical trial sites across India. Participants were stratified into three age groups (adults >18 years, children ≥5 to <18 years, and infants ≥1 to <5 years) and were randomised in a 3:1 ratio to receive either BBV131 or Shanchol™. All participants received two doses of the vaccine orally on days 0 and 14. Immunogenicity was assessed through blood samples collected at baseline, two weeks after each dose, and follow-ups at days 28, 56, 90, and 180. The primary endpoint focused on the proportion of participants achieving >4-fold increase in vibriocidal antibody titres against Ogawa and Inaba serotypes 14 days post two doses. While secondary endpoints included Geometric Mean Titre (GMT) measurements and safety. Safety was evaluated throughout the study, reporting solicited and unsolicited adverse events (AEs). Another cohort of 1800 was added to the above study as an addendum to expand the safety database.

FINDINGS

Of the 1800 enrolled participants, 1794 completed the study. Post-vaccination, the percentage of participants in the BBV131 group who exhibited a > 4-fold increase in anti-V. cholerae antibody titres were 68.25 % for Ogawa and 69.52 % for Inaba-demonstrating non-inferiority to Shanchol™, with a lower limit of 95 % CI above the non-inferiority margin. The safety profile revealed 257 AEs among 236 participants (13.1 %), with similar incidence across age groups and between vaccines; common AEs included dry mouth and headache.

INTERPRETATION

The findings indicate that BBV131 demonstrates non-inferior immunogenicity and comparable safety to Shanchol™ in healthy Indian adults and children, supporting its potential as an effective OCV.

CLINICAL TRIAL REGISTRATION

CTRI/2022/01/039734.

Dynamics of global emergency vaccine stockpiles: A systems analysis and application to cholera

BACKGROUND

The frequency and magnitude of infectious disease outbreaks are expected to rise. Although emergency vaccine stockpiles have emerged as a strategy to hedge against sporadic demand and accelerate response efforts, their long-term management is complex.

OBJECTIVE

This study investigates the role of global emergency vaccine stockpiles in achieving public health goals over time and underlying health system structures that drive their performance, with an application to cholera.

METHODS

A qualitative study design was used, combining insights from literature and semi-structured interviews with experts engaged in stockpile-related activities. A systems analysis, using qualitative causal loop diagrams, helps explain global stockpile behavior and discuss leverage points for change. It includes identifying system elements, important relationship between them, and resulting feedback loops.

FINDINGS

Despite expanding the stockpile for oral cholera vaccines, growing supply shortages since 2021 can partly be explained by increased demand due to a surge in outbreaks and the accumulation of evidence on vaccine effectiveness. These supply constraints have led to delays fulfilling vaccine orders for reactive campaigns and a pause on preventive use, leaving populations vulnerable. Despite ongoing efforts to scale-up production, a continued challenge is designing effective risk-sharing policies to attract manufacturers given uncertainty in demand forecasts and erratic orders. In literature, the time-dependent and complex environmental, social, demographic, and structural drivers that underpin the emergence and spread of disease are rarely jointly considered, making it difficult to anticipate the changing role and use of stockpiles relative to other preparedness strategies. Over time, global emergency vaccine stockpiles can support the transition from reactive to proactive strategies, helping achieve evolving public health goals towards disease elimination.

CONCLUSIONS

As disease epidemiology, vaccination strategies, uptake, and supply markets evolve asynchronously, there is a need for decision-support tools that better integrate supply and demand dynamics, hence expanding traditionally narrow model boundaries.

Geographic disparities impacting oral vaccine performance: Observations and future directions

Oral vaccines have several advantages compared with parenteral administration: they can be relatively cheap to produce in high quantities, easier to administer, and induce intestinal mucosal immunity that can protect against infection. These characteristics have led to successful use of oral vaccines against rotavirus, polio, and cholera. Unfortunately, oral vaccines for all three diseases have demonstrated lower performance in the highest-burden settings where they are most needed. Rotavirus vaccines are estimated to have >85% effectiveness against hospitalization in children <12 months in countries with low child mortality, but only ~65% effectiveness in countries with high child mortality. Similarly, oral polio vaccines have lower immunogenicity in developing country settings compared with high-resource settings. Data are more limited for oral cholera vaccines, but suggest lower titers among children compared with adults, and, for some vaccines, lower efficacy in endemic settings compared with non-endemic settings. These disparities are likely multifactorial, and available evidence suggests a role for maternal factors (e.g. transplacental antibodies, breastmilk), host factors (e.g. genetic polymorphisms-with the best evidence for rotavirus-or previous infection), and environmental factors (e.g. gut microbiome, co-infections). Overall, these data highlight the rather ambiguous and often contradictory nature of evidence on factors affecting oral vaccine response, cautioning against broad extrapolation of outcomes based on one population or one vaccine type. Meaningful impact on performance of oral vaccines will likely only be possible with a suite of interventions, given the complex and multifactorial nature of the problem, and the degree to which contributing factors are intertwined.

Knowledge and perception of a clinical trial among the participants: An experience from oral cholera vaccine study in Koshi Province, Nepal

Clinical trials (CT) have been the cornerstones in developing medicines, vaccines, and new interventions. Despite tremendous efforts, a CT cannot succeed without participants' involvement. Various factors can affect people's attitude and participation in a CT. Hence, this study was conducted to assess the knowledge and perception of a clinical trial among the participants of a CT at B.P. Koirala Institute of Health Sciences, Dharan, Nepal. This was a population-based descriptive cross-sectional study conducted during 2021-2022. Participants involved in a phase III clinical trial were enrolled, and an in-depth interview was conducted using a semi-structured questionnaire. Demographic information, knowledge and perception about CT were assessed, and a descriptive analysis was done. Among 622 participants, the majority were males (321; 51.6%), literate (587; 94.37%), of indigenous ethnic groups (Janajatis 61.4%), and without previous experience of CT (504; 81.1%). The majority had adequate knowledge (566/622; 91%) and positive perception (595/622; 95.7%) of CT. Most participants (467; 75.1%) had participated in CT to get protection from the particular disease from the provided vaccine and (603; 96.9%) believed CT to benefit mankind. Further studies comparing pre- and post-participation knowledge and perception might be helpful for planning and better management of CTs in such settings.

Parental motivations and perceived barriers to participating in pediatric vaccine clinical trials: Findings from the OCV-S trial in Nepal

Background

Pediatric vaccine clinical trials are crucial for evaluating and ensuring the safety and efficacy of new vaccines for children. However, in low-resource settings like Nepal, where clinical trials are relatively new, recruitment and retention of participants are challenging particularly due to diverse parental backgrounds, motivations and concerns. As such, parental motivations, perceived barriers, and experiences of participating in pediatric vaccine trial in Nepal, which hasn't previously been explored, needs to be understood.

Materials and Methods

We performed face-to-face exit interviews from April 6, 2022 to June 7, 2022, with parents whose children participated in the phase III clinical trial of the Oral Cholera Vaccine - Simplified (OCV-S) using a structured questionnaire on motivations for enrolling and barriers faced during the trial. Data were initially cleaned and encoded in Microsoft Excel before being analyzed with R version 4.3.1. Descriptive statistics were used to summarize demographic and other participants' characteristics. Bivariate and multivariate analyses, using odds ratios and their 95% confidence intervals, applying a significance level of 0.05 was used to analyze relationship between participant characteristics and trial experiences. Additionally, thematic analysis was performed on responses to open-ended questions.

Results

A total of 258 parents responded, out of which 252 (97.7 %) were first-time clinical trial participants with median age of 32 years. A majority, 196 (76.0 %), had a positive initial attitude towards the trial, and 204 (79.1 %) reported a positive overall experience. The primary motivations for participation included the potential health benefits for their children (56.2 %, n = 145). Despite 69 (26.7 %) participants receiving discouraging information from others, only 4 (5.8 %) were influenced by it. Most participants (n = 219, 84.9 %), felt that the trial had met their expectations. Challenges faced included loss of time (n = 30, 11.6 %) and missed school for children (n = 22, 8.5 %). Nonetheless, 179 participants (69.4 %) expressed a willingness to enroll their children in future trials. Participants who received specific details about the study before visiting the study site were significantly more likely to report positive experience, with an adjusted odds ratio of 1.97 (95 % CI: 1.03 - 3.72).

Conclusion

Majority of parents were supportive of their children's participation in the OCV-S trial, motivated largely by anticipated health benefits for their child. Key barriers identified included logistical issues, costs (both financial and opportunity costs), misinformation, and concerns about trial procedures and potential side effects. Focus on reducing logistical and participation-related burdens, catering of trial-specific information, enhancing the clarity of the informed consent process, addressing safety concerns proactively and implementing continuous follow-up can help improve participation rates and retention in future trials. The high level of enthusiasm for clinical trials among parents, despite these barriers, highlights the promising potential for future research endeavors in Nepal.