Vaccination Considerations for Business Travelers
Vaccination Considerations for Business Travelers
Japanese encephalitis (JE) virus is a flavivirus transmitted by Culex mosquitoes, endemic in Asia and parts of the western Pacific, and usually affects children living in rural areas. Infections can lead to fever, headache, mental status change, seizures, vomiting and acute encephalitis or aseptic meningitis. Case fatality rate is 20–30%; 30–50% can develop long-term neuropsychological problems.
JE is estimated to cause <1 case per million travelers, and only 57 JE cases were reported in residents from nonendemic countries between 1973 and 2011. Nevertheless, vaccination can prevent the potentially devastating sequelae. Business travelers who plan to spend significant periods of time in endemic countries, stay in rural areas or plan long or repeated trips may have exposure to JE.
A Vero cell-derived inactivated JE vaccine (JE-VC; Ixiaro®, Intercell, Vienna, Austria) was licensed in 2009 as a two-dose series administered on days 0 and 28. After the primary series, seroprotection rates were 83, 58 and 48% at months 6, 12 and 24, respectively. A booster dose at month 11 and/or month 23 achieved 100% seroconversion (Table 1). A single-dose immunization (incomplete primary immunization) led to seroprotection in only 40% of the volunteers 1 month later and 9% of the volunteers at month 6; however, a booster dose at month 11 led to seroconversion in 99% of the volunteers. Therefore, travelers who initiate primary immunization can complete their series at 11 months. Moreover, travelers who previously received the older mouse brain-derived JE vaccine series (JE-MB; JE-Vax®, Biken, Osaka, Japan) and then were vaccinated with JE-VC had excellent seroprotection rates after a single dose of JE-VC (95–100%) compared with nonprimed travelers (39–42%) who received a single dose of JE-VC. Thus, only one booster dose of JE-VC in persons previously vaccinated with JE-MB provides adequate protection, although duration of protection is unknown.
A chimeric JE vaccine (JE-CV) has also been developed and has become available in Australia. At 28 days following the single dose of JE-CV, 99% of the vaccine recipients achieved seroprotective antibody levels, and seroprotection persisted to month 60 in >80% of the JE-CV vaccinees.
Japanese Encephalitis
Japanese encephalitis (JE) virus is a flavivirus transmitted by Culex mosquitoes, endemic in Asia and parts of the western Pacific, and usually affects children living in rural areas. Infections can lead to fever, headache, mental status change, seizures, vomiting and acute encephalitis or aseptic meningitis. Case fatality rate is 20–30%; 30–50% can develop long-term neuropsychological problems.
JE is estimated to cause <1 case per million travelers, and only 57 JE cases were reported in residents from nonendemic countries between 1973 and 2011. Nevertheless, vaccination can prevent the potentially devastating sequelae. Business travelers who plan to spend significant periods of time in endemic countries, stay in rural areas or plan long or repeated trips may have exposure to JE.
A Vero cell-derived inactivated JE vaccine (JE-VC; Ixiaro®, Intercell, Vienna, Austria) was licensed in 2009 as a two-dose series administered on days 0 and 28. After the primary series, seroprotection rates were 83, 58 and 48% at months 6, 12 and 24, respectively. A booster dose at month 11 and/or month 23 achieved 100% seroconversion (Table 1). A single-dose immunization (incomplete primary immunization) led to seroprotection in only 40% of the volunteers 1 month later and 9% of the volunteers at month 6; however, a booster dose at month 11 led to seroconversion in 99% of the volunteers. Therefore, travelers who initiate primary immunization can complete their series at 11 months. Moreover, travelers who previously received the older mouse brain-derived JE vaccine series (JE-MB; JE-Vax®, Biken, Osaka, Japan) and then were vaccinated with JE-VC had excellent seroprotection rates after a single dose of JE-VC (95–100%) compared with nonprimed travelers (39–42%) who received a single dose of JE-VC. Thus, only one booster dose of JE-VC in persons previously vaccinated with JE-MB provides adequate protection, although duration of protection is unknown.
A chimeric JE vaccine (JE-CV) has also been developed and has become available in Australia. At 28 days following the single dose of JE-CV, 99% of the vaccine recipients achieved seroprotective antibody levels, and seroprotection persisted to month 60 in >80% of the JE-CV vaccinees.
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