Effectiveness of a single dose of Japanese encephalitis vaccine among adults, Assam, India, 2012-2018

A Special Insight on the Causal Agents and Mode of Occurrence of Japanese Encephalitis (JE) Infections in Rural Regions of Assam, India

INTRODUCTION

Japanese Encephalitis (JE) is a life-threatening disease, especially in the Indian subcontinent. Knowledge about the nature and ecology of the dispersal of JE virus (JEV) vectors needs to be increased. This study mechanistically explores the ecology of JEV vectors and the mode and frequency of occurrence of Acute Encephalitis Syndrome (AES) and JEV infections.

METHODS

We established a linear relationship between environmental variables and JEV infection by JEV vectors (mosquitoes)-Culex tritaeniorhynchus, Culex vishnui, and Culex pseudovishnui. The relative abundance of three mosquito species was evaluated, and the JE Sample Positivity Rate (SPR) and JE Case Fatality Rate (CFR) were computed.

RESULTS

Culex vishnui had a high abundance in residential areas during the transition from hot-dry (77.34%) to hot-wet period (78.66%) at temperatures between 31°C and 34°C and relative humidity of 80%-85.3%; this period also coincided with occurrence of AES (39 cases in hot-dry and 88 cases in hot-wet period) and JE (8 instances in hot-dry and 31 cases in hot-wet period). JE infection dominated near rainfed rice fields (rainfall: R = 0.67 at p < 0.05; rainy days: R = 0.74, p < 0.01). SPR was up to 32.28%, and CFR was as high as 42.86%; JEV infection was concentrated in adult male humans near rice fields (15.66%).

CONCLUSIONS

Climate modulation over the years can influence the distribution of Culex vishnui and, hence, AES and JE cases. JEV infections tend to rise in JE hotspot regions, especially near rice fields. Thus, comprehensive epidemiological investigations will help prevent a silent outbreak of JE.

Effectiveness of interventions to improve vaccine efficacy: a systematic review and meta-analysis

BACKGROUND

Vaccination is a crucial public health intervention that has significantly reduced the incidence of infectious diseases. Vaccine-related interventions refer to strategies implemented to enhance vaccination uptake, coverage, and effectiveness, like modes of delivery, types or dosages. Despite extensive research on vaccine efficacy, a comprehensive analysis of the variability in vaccine effectiveness across different interventions, settings, and populations is limited. This study aims to systematically review and meta-analyze the impact of various Vaccine-Related Interventions (VRIs).

METHODS

This review included 139 randomized controlled trials, cohort, and case-control studies evaluating VRIs from January 2015 to December 2023. The risk of bias was assessed using the ROB-2 and ROBINS-E tools. Statistical analyses were conducted to evaluate overall effect sizes, infection rates, and heterogeneity and subgroup analysis.

RESULTS

Of the 139 studies reviewed, 97 were included in the meta-analysis, comprising approximately 1.4 million participants. Populations across various settings were analyzed, with median vaccinated population sizes for the 1st dose (4598, IQR = 15,749), 2nd dose (6214, IQR = 13,817), and 3rd dose (3508, IQR = 5546). The overall total vaccinated population had a median of 4370 and an IQR of 16,475. The interventions showed a significant positive effect on vaccine efficacy, with an estimated effect size of 0.6432 (95% CI 0.4049 to 0.8815). Heterogeneity was negligible, with Tau2 = 0, I2 = 0.00%, and H2 = 1.00. The Galbraith plot suggested minimal variability. The study utilized ROB-2 and ROBINS-E tools to evaluate bias, with Egger's test (t = - 0.9941, p = 0.3227) confirming no significant publication bias. The funnel plot indicated minimal bias in the included studies.

CONCLUSION

The study supports the effectiveness of vaccine-related interventions in enhancing vaccine efficacy. The negligible heterogeneity and consistent effect sizes across diverse populations and settings provide a robust basis for implementing public health strategies aimed at improving vaccination outcomes.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42024543608.

Adult vaccination in India: A rapid review of current status & implementation challenges

Background & objectives The expanded programme on immunization launched in India in 1978, with its focus on preventing six diseases in children (tetanus, diphtheria, pertussis, poliomyelitis, typhoid, and childhood tuberculosis), was widened in its scope in 1985-86. This new avtaar, the Universal Immunization Programme (UIP), incorporated measles vaccine for children and rubella and adult diphtheria vaccines for pregnant women. We conducted this rapid review on adult immunization relevant for India, as recent COVID-19 experience revealed how newly emergent or re-emergent pathogens could have their onslaughts on the elderly and adults with comorbidities. Methods Three different bibliographic databases, namely PubMed, Scopus and Ovid were searched electronically to access the articles published in peer-reviewed journals. Relevant consensus guidelines by in-country professional groups were also collated. We conducted deduplication and screening of the outputs of these searches (1242 bibliographical records). Finally, 250 articles were found eligible for inclusion. As trials on the reduction of morbidities, mortalities and hospitalizations in adults due to proposed vaccines under Indian consensus guidelines were not available, no meta-analysis was conducted. Results Evidence from articles finally included in this synthesis were grouped under (i) preventing viral and bacterial infections in adults; (ii) adult vaccination and awareness tools; (iii) vaccine hesitancy/acceptance; and (iv) adult vaccination guidelines. In-country research revealed the need for introducing the Human Papilloma Virus (HPV) vaccine in adolescence or early-adulthood to prevent ano-genital cancers in elderly and later life. Importantly HPV prevalence among cervical cancer patients varied between 88 to 98 per cent in Andhra Pradesh, Odisha and Delhi. The importance of conducting regular surveillance of pneumococcal diseases and influenza, as well as tweaking the vaccines accordingly, was revealed in other articles. A poor uptake of influenza vaccine (≤2%) in adults (≥45 yr) was documented. The uptake of hepatitis B vaccine in Health Care Workers (HCWs) in Delhi and Mumbai was of concern and ranged from 55 to 64 per cent. The vulnerability of HCWs to rubella was investigated in a paediatric ophthalmic hospital in Madurai: a tenth of the selected HCWs were rubella seronegative and mounted good protective immunity following RA 27/3 vaccine administration. An outbreak of measles in college students in Pune emphasized the phenomenon of waning immunity. Similarly, a study in the infectious disease hospital in Kolkata and in-patients in Delhi revealed a lack of protective immunity against diphtheria and tetanus in adults. The researchers estimated the economic benefits of providing a typhoid vaccine to a household to be US$ 23 in a middle-income neighbourhood and US$ 14 in slum settings. The authors highlighted the importance of preventive strategies, finding that the cost of severe typhoid fever was US$ 119.1 in 18 centres across India. Both qualitative and quantitative investigations explored vaccine hesitancy, which was studied more during the COVID-19 pandemic than earlier. Interpretation & conclusions Vaccination programmes in India would require (i) increasing awareness around vaccine-preventable diseases among adults and HCWs; (ii) actively engaging health care systems and community-based organizations; and (iii) developing and producing affordable, safe, and country-appropriate vaccines. Effective communication strategies and tools will be the key to the success of such interventions.

Cost-effectiveness Analysis of Japanese Encephalitis Vaccination for Children <15 Years of Age, Bangladesh

Japanese encephalitis (JE) is preventable using the affordable, effective, and safe live attenuated SA 14-14-2 JE vaccine (CD-JEV). We used a Markov model to evaluate the cost-effectiveness of 1 dose of CD-JEV compared with no vaccination in 3 vaccination strategies in Bangladesh: subnational campaign and routine immunization, subnational campaign and national routine immunization, and national routine immunization alone. For input parameters, we gathered information from a cost-of-illness study, medical literature, government documents, and expert opinions. The base-case analysis estimated that a subnational campaign for children <15 years of age and routine immunization over 20 birth cohorts in Rajshahi, Rangpur, and Chattogram yielded (in 2021 US dollars) a cost of $82.2 million, $981/disability-adjusted life years averted, $9,964/case averted, and $49,819/death averted (societal perspective). We projected CD-JEV vaccination would be cost-effective across cost perspectives and vaccination strategies in Bangladesh, yielding an incremental cost-effectiveness ratio of approximately one third of per capita national gross domestic product.

The durability of vaccine-induced protection: an overview

INTRODUCTION

Current vaccines vary widely in both their efficacy against infection and disease, and the durability of the efficacy. Some vaccines provide practically lifelong protection with a single dose, while others provide only limited protection following annual boosters. What variables make vaccine-induced immune responses last? Can breakthroughs in these factors and technologies help us produce vaccines with better protection and fewer doses? The durability of vaccine-induced protection is now a hot area in vaccinology research, especially after COVID-19 vaccines lost their luster. It has fueled discussion on the eventual utility of existing vaccines to society and bolstered the anti-vaxxer camp. To sustain public trust in vaccines, lasting vaccines must be developed.

AREAS COVERED

This review summarizes licensed vaccines' protection. It analyses immunological principles and vaccine and vaccinee parameters that determine longevity of antibodies. The review concludes with challenges and the way forward to improve vaccine durability.

EXPERT OPINION

Despite enormous advances, we still lack essential markers and reliable correlates of lasting protection. Most research has focused on humoral immune responses, but we must also focus on innate, mucosal, and cellular responses - their assessment, correlates, determinants, and novel adjuvants. Suitable vaccine designs and platforms for durable immunity must be found.

Incidence of Japanese Encephalitis and Acute Encephalitis Syndrome Hospitalizations in the Medium-Endemic Region in Central India

BACKGROUND

We estimated the incidence of Japanese encephalitis (JE) and acute encephalitis syndrome (AES) following routine immunization with the live-attenuated SA 14-14-2 JE vaccine.

METHODS

We implemented enhanced surveillance of AES and JE hospitalizations in endemic districts in Maharashtra and Telangana States during 2015-2016 and 2018-2020. We estimated incidence and compared differences in the incidence of JE and AES between two states, and vaccinated and unvaccinated districts during two study periods. We also considered secondary data from public health services to understand long-term trends from 2007 to 2020.

RESULTS

The annual AES incidence rate of 2.25 cases per 100,000 children in Maharashtra during 2018-2020 was significantly lower than 3.36 cases per 100,000 children during 2015-2016. The six JE-vaccinated districts in Maharashtra had significantly lower incidence rates during 2018-2020 (2.03, 95% CI 1.73-2.37) than in 2015-16 (3.26, 2.86-3.70). In addition, the incidence of both JE and AES in two unvaccinated districts was higher than in the vaccinated districts in Maharashtra. Telangana had a lower incidence of both JE and AES than Maharashtra. The AES incidence rate of 0.95 (0.77-1.17) during 2018-2020 in Telangana was significantly lower than 1.67 (1.41-1.97) during 2015-2016.

CONCLUSIONS

The annual incidence rate of Japanese encephalitis was < 1 case per 100,000 children. It indicated accelerated control of Japanese encephalitis after routine immunization. However, the annual incidence of acute encephalitis syndrome was still > 1 case per 100,000 children. It highlights the need for improving surveillance and evaluating the impacts of vaccination.

Coverage of Japanese encephalitis routine vaccination among children in central India

We aimed to estimate the coverage of Japanese encephalitis (JE) vaccination in central India to help explain the continued occurrence of JE disease despite routine vaccination. We implemented a 30-cluster survey for estimating the coverage of JE vaccination in the medium-endemic areas implemented with JE vaccination in central India. The parents were enquired about the uptake of the JE vaccine by their children aged 2-6 years, followed by verification of the immunization cards at home along with reasons for non-vaccination. Vaccination coverage was reported as a percentage with 95% confidence intervals (CI). We estimated high coverage of live-attenuated SA 14-14-2 JE vaccination in Maharashtra (94.8%, 95% CI: 92.7-96.3) and Telangana (92.8%, 95% CI: 90.0-94.9). The vaccination card retention was 90.3% in Maharashtra and 70.4% in Telangana state. There were no gender differences in coverage in both states. A similar level of JE vaccination coverage was observed during the year 2013-2021 in both states. In Maharashtra, the maximum age-wise coverage was 96.6% in the >60 months age category, whereas in Telangana it was in the <24 months age category (97.2%). The timeliness of JE vaccination was appropriate and similar in both states. We found a very good agreement between JE and measles-rubella vaccinations administered simultaneously. The reasons for non-vaccination were the shortage of vaccines and the parental migration for work. The coverage of JE vaccination was high in medium-endemic regions in central India. Vaccination effectiveness studies may help further explain the continued incidence of JE.

Global emergence of West Nile virus: Threat & preparedness in special perspective to India

West Nile virus (WNV) is a mosquito-borne single-stranded RNA neurotropic virus within the family Flaviviridae. The virus was first reported in the West Nile province of Uganda in 1937. Since then, sporadic cases have been reported until the last two decades when it has emerged as a threat to public health. The emergence of WNV with more severity in recent times is intriguing. Considering this phenomenon, the WNV-affected areas of the world were distinguished as old versus new in a depicted world map. The present review showcases the historical and epidemiological perspectives of the virus, genetic diversity of prevailing lineages and clinical spectrum associated with its infection. Emergence of the virus has been discussed in special context to India because of co-circulation of different WNV lineages/strains along with other flaviviruses. Recent laboratory diagnostics, vaccine development and clinical management associated with WNV infection have also been discussed. Further, the research gaps, especially in context to India have been highlighted that may have a pivotal role in combating the spread of WNV.