2016-01-12-世界卫生组织-Japanese_Encephalitis_Vaccine_Information_sheet_5页_136kb

Japanese Encephalitis Vaccine Information Summary

The document provides an overview of the Japanese encephalitis (JE) vaccines, including their types, compositions, and observed rates of vaccine-related adverse events. JE vaccines are categorized as inactivated, live attenuated, or live recombinant, and are used to prevent JE, a viral disease that can cause severe neurological complications. The summary below outlines the key details.

Vaccine Types and Compositions

There are three main types of JE vaccines:

• Inactivated vaccines: These include Vero-cell-derived vaccines (e.g., IC51/IXIARO and JEEV) and mouse-brain-derived vaccines. Inactivated vaccines are grown in cells (Vero or primary hamster kidney) and inactivated with formaldehyde or gelatin. WHO prequalification applies to some.
• Live attenuated vaccine: The SA14-14-2 vaccine uses a neuro-attenuated strain of JE virus. It is produced from primary hamster kidney cells. Licensed in China and prequalified by WHO; used in many Asian countries.
• Live recombinant vaccine: One product licensed in Australia (IMOJEV) and some Asian countries. It combines JE antigenic determinants with the yellow fever 17D virus as a vector.

Adjuvants and stabilizers vary: inactivated Vero-cell vaccines use aluminum hydroxide, while mouse-brain-derived and live vaccines use gelatin. Thiomersal may be present as a preservative.

Observed Rates of Adverse Events

Adverse events are classified into local, systemic, serious, and neurological categories.

• Local reactions: Common at injection sites, including pain, redness, swelling, and tenderness. Rates vary: 40% for Vero-cell-derived in adults, up to 60% for mouse-brain-derived, 40-44% for live attenuated in children, and 10% for live recombinant.
• Systemic reactions: Include fever, headache, fatigue, muscle pain, and flu-like symptoms. Most are mild to moderate. Rates per 100 doses: Vero-cell-derived around 40-40%, mouse-brain-derived 5-30%, live and live recombinant 45-53%.
• Serious adverse events: Primarily hypersensitivity reactions, such as generalized urticaria or anaphylaxis. Frequencies: 18-64 per 10,000 doses for mouse-brain-derived, and up to 2 per million doses for anaphylaxis. Risk factors include allergies or asthma. Live attenuated and recombinant vaccines show no or low reports.
• Neurological adverse events: Rare but significant. Inactivated Vero-cell vaccines have no increased risk; mouse-brain-derived have up to one case of acute disseminated encephalomyelitis (ADEM) per 50,000-75,000 doses, and very rare cases of encephalitis or other neurological issues. Live attenuated vaccine showed no severe neurological events in trials.
• Vaccine-associated JE disease: No cases reported in a 20-year review.

Key risks highlight the potential for allergic reactions, especially with mouse-brain-derived vaccines, and the need for careful consideration when administering to specific populations. The live recombinant vaccine is generally well-tolerated but data on rare neurological events are limited post-marketing. General surveillance and studies emphasize that most adverse events are mild and transient.

WHO and other references are cited in the full document for detailed data.