Also adults without a reliable history of having had chickenpox. Flu occurs throughout the year in the tropics, during December to April in the northern hemisphere, and during April to September in the southern hemisphere. For all travelers. After primary immunization, a booster in six to twelve months is recommended for long-term protection. For all health care personnel, those dwelling over six months, if daily physical contact with the people is anticipated, or if emergency health care facilities are substandard.
Full immunization requires three injections over six months.
Single injection for those two years old or more. Not needed for Hong Kong and Singapore. Occurs seasonally by regions in rural areas. Primary series of three injections over one month. Vaccination should only be considered for persons who plan to live in area where it is endemic or epidemic and for travelers whose activities include trips into rural, farming areas if dwelling in rural areas.