This is an active electronic surveillance using data from the Defense Medical Surveillance System (DMSS) to detect and characterize serious, rare adverse events occurring within 42 days after vaccination with the Japanese Encephalitis Vaccine IXIARO within the US Military, to detect adverse events that occur more frequently after IXIARO and to electronically follow up pregnancies during or shortly before which IXIARO was administered.

There will be no intervention and no individuals contacted.

Inclusion Criteria:

• Male and female active duty U.S. military personnel ≥ 17 years of age who either received at least one dose of IXIARO (IXIARO exposed group) or at least one dose of JE-VAX (comparison group).

Exclusion Criteria:

• Individuals who have an ICD-9-CM code suggestive of one of the predefined adverse events screened for in IC51-401 prior to vaccination with IXIARO cannot with certainty be classified as being "disease free" at study entry and will be excluded for that adverse event.

Active duty military personnel (Army, Navy, Air Force, and Marines) who are ≥17 years of age and received at least one dose of Japanese encephalitis vaccine.