# Japanese Encephalitis Vaccine in Low- and Middle-Income Countries (LMICs): A Narrative Review of Efficacy, Effectiveness, Safety, Cost, and Policy

## TL;DR

This paper reviews Japanese Encephalitis vaccines in low- and middle-income countries, focusing on their effectiveness, safety, cost, and policy implications.

## Contribution

The paper provides a comprehensive review of Japanese Encephalitis vaccine efficacy and cost-effectiveness in low- and middle-income countries, highlighting policy recommendations.

## Key findings

- JE vaccines show high efficacy and strong safety profiles with mild adverse effects like fever.
- The live attenuated SA 14-14-2 vaccine is cost-effective and reduces healthcare expenditures in endemic regions.
- Tailored policies and financial support are needed for sustainable vaccination programs in LMICs.

## Abstract

Japanese Encephalitis (JE) is a mosquito-borne viral infection that causes acute brain inflammation. First identified in Japan in 1871, the disease gained renewed global attention in 2025 after emerging in a non-endemic region, raising significant healthcare concerns. Vaccination remains the most effective strategy for preventing outbreaks. However, low- and middle-income countries (LMICs) face considerable challenges in implementing vaccination programs due to geographical, economic, and regulatory barriers. Most existing studies on JE vaccines (JEVs) have been conducted in higher-income countries, leaving critical gaps in data on efficacy and safety in LMIC settings. Furthermore, uncertainties surrounding cost-effectiveness make funding decisions more complex. This narrative review evaluates the current evidence on JE vaccination in LMICs, based on a literature search in PubMed and ScienceDirect covering 2005–2025. The review examines vaccine efficacy, safety, cost-effectiveness, and policy implementation. Findings show that JEVs demonstrate high efficacy and strong safety profiles, with mild adverse effects, most commonly fever. The live attenuated SA 14-14-2 vaccine (LAJEV) is particularly cost-effective, offering substantial economic benefits by reducing healthcare expenditures in endemic regions. To ensure sustainability, vaccination programs in LMICs require tailored policies and targeted financial support. Policy frameworks must be adapted to local contexts, enabling focused, effective, and equitable implementation.