A model immunization programme to control Japanese encephalitis in Viet Nam.

Area of Science:

• * Public Health
• * Vaccinology
• * Epidemiology

Background:

• * The existing Japanese encephalitis (JE) vaccine program in Vietnam, targeting children under 5 years old with three pediatric doses since 1997, has not sufficiently reduced JE incidence.
• * High JE rates persist, notably in the 5-9 year-old demographic, indicating a gap in the current vaccination strategy.

Purpose of the Study:

• * To evaluate the feasibility and impact of a modified JE immunization program.
• * To assess the effectiveness of administering JE vaccine to children aged 1-9 years using a three-dose regimen with adjusted pediatric and adult doses.

Main Methods:

• * Implementation of a model JE immunization program in selected districts targeting children aged 1-9 years.
• * Utilized a three-dose regimen: pediatric doses for those under 3 years and adult doses for those 3 years and older.
• * Achieved a high immunization coverage of 96.2% with at least two vaccine doses among targeted children.

Main Results:

• * Districts participating in the model program experienced a substantial decline in JE incidence rates, from 11.32 to 0.87 per 100,000.
• * The most significant reduction in JE incidence was observed in the 5-9 year-old age group.
• * The model program demonstrated high vaccine uptake, with 96.2% of targeted children receiving two or more doses.

Conclusions:

• * Expanding JE vaccination to include children up to 9 years old is effective in reducing disease incidence.
• * A policy recommendation to incorporate 5-9 year olds into catch-up immunization campaigns is proposed.
• * Administering a fourth JE vaccine dose to children aged 5-9 who received the initial three doses early in life is suggested for sustained protection.