There is no single schedule for the administration of immunizing agents to travellers. Each schedule must be personalized according to the individual traveller's immunization history, the countries to be visited, the type and duration of travel, and the amount of time available before departure.

It is important to remember that the most frequent health problems faced by international travellers are not preventable by vaccines. It is also important to remember that immunization is not a substitute for careful selection and handling of food and water.

A health care provider or travel medicine clinic should be consulted 2 to 3 months in advance of travel in order to allow sufficient time for optimal immunization schedules to be completed.

A listing of travel clinics across Canada can be found at the Public Health Agency of Canada's Travel Medicine Program at www.travelhealth.gc.ca.

Travel is a good opportunity for the health care provider to review the immunization status of infants, children, adolescents and adults. Unimmunized or incompletely immunized travellers should be offered vaccination as recommended in the Canadian Immunization Guide, 7^th Edition 2006.

Routine Immunizations

The following section specifically discusses the indication for "extra" or booster doses of routine immunizations or a change in the routine immunization schedule as it applies to travellers.

Accelerated primary vaccination schedule - infants

For infants embarking on travel, the primary vaccination series with diphtheria, tetanus, acellular pertussis, polio, Haemophilus influenzae type b (DTaP-IPV-Hib) and pneumococcal conjugate can be started as young as 6 weeks of age.

Hepatitis B - adults

Travel is a good opportunity to offer hepatitis B immunization to adults who have not been previously vaccinated. It should be recommended particularly to travellers who will be residing in areas with high levels of endemic hepatitis B or working in health care facilities, and those likely to have contact with blood or to have sexual contact with residents of such areas.

Hepatitis B - infants and children

The age at which infants, children and adolescents are offered hepatitis B vaccine varies from jurisdiction to jurisdiction in Canada. Since hepatitis B carrier rates are much higher in developing countries, every effort should be made to arrange full hepatitis B immunization for children of any age who will live in an area where hepatitis B is endemic.

Measles, mumps, rubella - adults

Measles, mumps and rubella are endemic in many countries. Protection against measles is especially important for people planning foreign travel, including adolescents and adults who have not had measles disease and have not been adequately immunized. Two doses of measles-containing vaccine (MMR) are recommended for all unimmunized adult travellers who were born in or after 1970 and who are en route to a measles-endemic area, unless there is serologic proof of immunity or physician documentation of prior measles. Similarly, protection against rubella is especially important for women of childbearing age who are not immune to the disease.

Measles - infants and children

Measles vaccine should be given at an earlier age than usual for children travelling to countries where measles is endemic. Measles-containing vaccine (MMR) may be given as early as 6 months of age, but then the routine series of two doses must still be re-started after the child is 12 months old.

Pertussis

For adults who have not previously received a dose of acellular pertussis vaccine, it is recommended that the tetanus and diphtheria booster dose (Td) be replaced by the combined Tdap vaccine.

Poliomyelitis

The risk of polio for travellers has substantially decreased as we move towards global polio eradication. A single booster dose of poliomyelitis vaccine (IPV) in adulthood is recommended for international travellers who plan to visit regions of the world where poliovirus continues to circulate in either epidemic or endemic fashion. The need for subsequent boosters of poliovirus vaccine has not been established.

Tetanus and diphtheria - adults

Adult travellers should be vaccinated against tetanus and diphtheria with a Td vaccine booster dose every 10 years for optimal protection.

Required Immunizations

The following may be a requirement of international law, or proof of immunization may be considered a visa requirement.

Cholera

Cholera vaccine has not been required for border crossing under International Health Regulations since 1973. Some travellers to parts of Africa have reported being asked to provide a certificate of immunization against cholera. This "requirement" is not usually the policy of the national government but, rather, of local authorities. Given the related risks of immunization in some countries, certain travel clinics provide a cholera "exemption certificate", which is used to help travellers avoid being given cholera vaccine while abroad.

Meningococcal disease

As a condition of entry, Saudi Arabia requires proof of meningococcal immunization for pilgrims to Mecca during the Hajj. Quadrivalent polysaccharide vaccine is recommended. For other indications for this vaccine see the Canadian Immunization Guide, 7^th Edition 2006, Recommended Usage section in the Meningococcal Vaccine chapter.

Yellow fever

Yellow fever is the only vaccine required as a condition of entry under the World Health Organization's International Health Regulations. A valid International Certificate of Vaccination, issued within the previous 10 years, is mandatory for entry into certain countries in Africa and South America. Other countries have requirements for proof of immunization from travellers who have passed through yellow fever endemic zones. Please refer to the Canadian Immunization Guide, 7^th Edition 2006 maps in the Yellow Fever Vaccine chapter for more information.

The period of validity of the International Vaccination Certificate for yellow fever is 10 years, beginning 10 days after primary vaccination and immediately after re-vaccination. Only Yellow Fever Vaccination Centre clinics designated by PHAC can provide the International Certificate of Vaccination in Canada. A list of these centres can be obtained from PHAC's Travel Medicine Program Web site (http://www.travelhealth.gc.ca).

The decision to immunize against yellow fever will depend on the itinerary of the individual traveller and the specific requirements of the country to be visited (including stopovers). As well as being necessary for entry into certain countries, immunization against yellow fever is recommended for all travellers who are visiting or living in countries in Africa and South America where yellow fever infection is officially reported. It is also recommended for travel outside of urban areas in countries that do not officially report yellow fever but lie in the yellow fever endemic zones.

Recommended Immunizations

On the basis of a risk assessment of the itinerary, the style of travel and the traveller's underlying health, the following vaccines should be considered in consultation with a health care provider.

Bacille Calmette-Guérin (BCG)

Immunization with BCG may be considered for travellers planning extended stays in areas of high tuberculosis prevalence, particularly where a program of serial skin testing and appropriate chemoprophylaxis may not be feasible or where primary isoniazid resistance of Mycobacterium tuberculosis is high. Travellers are advised to consult a specialist in travel medicine or infectious diseases when considering a decision for or against BCG immunization. Please refer to the Canadian Immunization Guide, 7^th Edition 2006, Bacille Calmette-Guérin Vaccine chapter for more information.

Cholera

In specific, limited circumstances (e.g., high-risk ex-patriots such as relief and aid workers or health professionals working in endemic countries), the oral cholera vaccine (Chol-Ecol-O, Dukoral™) may be considered. A detailed, individual risk assessment should be made in order to determine which travellers may benefit from immunization.

The Chol-Ecol-O vaccine has been shown to provide limited, short-term protection against diarrhea caused by enterotoxigenic Escherichia coli. A detailed, individual risk assessment should be made in order to determine which travellers may benefit the most from this vaccine as a preventive strategy for travellers' diarrhea. Please refer to theCanadian Immunization Guide, 7^th Edition 2006, Cholera Vaccine chapter for more information.

Hepatitis A

Hepatitis A is the most common vaccine-preventable disease in travellers. Protection against hepatitis A is highly recommended for all travellers to developing countries, especially to rural areas or places with inadequate sanitary facilities in countries where the disease is endemic. Protective antibodies are detectable within 2 weeks of administration. Given the long incubation period of hepatitis A (2 to 7 weeks), the vaccine can be administered up to the day of departure and still protect the majority of travellers.

The advent of active immunizing agents has made the use of immune globulin virtually obsolete for the purposes of travel prophylaxis. The only exceptions would be people for whom hepatitis A immunization is contraindicated or may not be effective (e.g., immunocompromised travellers and infants < 1 year of age). Immune globulin provides protection for only 3 to 5 months and should be given immediately before departure.

Influenza

People at high risk of influenza complications embarking on foreign travel to destinations where influenza is likely to be circulating should be immunized with the most current available vaccine. Influenza transmission is enhanced in the crowded conditions associated with air travel, cruise ships and tour groups. In the tropics, influenza can occur throughout the year. In the southern hemisphere, peak activity occurs from April through September and in the northern hemisphere from November through March. Vaccines prepared specifically against strains that are predicted to circulate in the southern hemisphere are not currently available in Canada.

Japanese encephalitis

Japanese encephalitis is the leading cause of viral encephalitis in Asia, but the disease is rare in travellers. Its incidence has been decreasing in China, Korea and Japan but increasing in Bangladesh, India, Nepal, Pakistan, northern Thailand and Vietnam. It occurs in epidemics in late summer and early fall in temperate areas and sporadically throughout the year in tropical areas of Asia. Immunization should generally be considered for those who will spend 1 month or more in endemic or epidemic areas during the transmission season, especially if travel will include rural areas. In special circumstances, immunization should be considered for some people spending < 1 month in endemic areas, e.g., travellers to areas where there is an epidemic, travellers making repeated short trips or people with extensive outdoor rural exposure.

Meningococcal disease - adults

Quadrivalent meningococcal polysaccharide vaccine is recommended for travellers planning a prolonged stay in areas with a high incidence of meningococcal disease. Short-term travellers (< 3 weeks) on business or holiday (including safaris) who will have little contact with local populations are at minimal risk, and therefore immunization is not routinely recommended. When doubt about the nature of exposure exists, it may be prudent to offer immunization. However, in special circumstances, immunization should be considered for short-term travellers if (a) there will be close contact with the local population in endemic areas, (b) there will be travel to epidemic areas or (c) the traveller will be providing health care to others.

As noted previously, proof of meningococcal immunization may be required by certain countries e.g., Saudi Arabia for pilgrims to Mecca during the Hajj. Outbreaks of meningococcal disease have affected these pilgrims in the past, involving serogroup A in 1987, and both serogroups A and W135 in 2000 and 2001.

Meningococcal conjugate C vaccine was approved in Canada in 2001. This vaccine only protects against serogroup C and therefore is not appropriate for protection of travellers, as it does not protect against serogroups A, Y or W135. Travelers should therefore receive a quadrivalent vaccine that provides protection against serogroups A, C, Y and W135.

Meningococcal disease - infants and children

Because of the relative inability of very young children to respond to polysaccharide vaccine, infants aged 2 to 12 months should be immunized with the appropriate doses of meningococcal C conjugate based on age and vaccine manufacturer, if not previously received. However, bivalent meningococcal polysaccharide AC vaccine or quadrivalent ACYW135 may be considered for children as young as 3 months who are travelling to regions where broader protection is needed. Please refer to the Canadian Immunization Guide, 7^th Edition 2006, Meningococcal Vaccine chapter for more information.

Rabies

Pre-exposure immunization should be considered for travellers intending to live or work in areas where rabies is enzootic and rabies control programs for domestic animals are inadequate, or where adequate and safe post-exposure management is not available. Children, particularly those who are too young to understand the need to avoid animals or to report bites, should also be considered for pre-exposure immunization. After exposure to a rabid animal, administration of two additional doses of rabies vaccine is imperative as soon as possible. For someone who has received a full course of pre-exposure immunization, rabies immune globulin is not indicated. Please refer to the Canadian Immunization Guide, 7^th Edition 2006, Rabies Vaccine chapter for more information.

Typhoid

Typhoid vaccine is recommended for travellers who will have prolonged exposure (> 4 weeks) to potentially contaminated food and water, especially those travelling to smaller cities and villages or rural areas off the usual tourist itineraries in countries with a high incidence of disease. Individuals billeted with or visiting families in such areas may be at particularly high risk. Immunization should also be considered for travellers with reduced or absent gastric acid secretion. Immunization is not routinely recommended for business travel or short-term (< 4 weeks) holidays in resort hotels in such countries. Parenteral inactivated and live oral vaccines are available.

Travellers who are immunodeficient

In general, live vaccines should be avoided in individuals who are immunodeficient. These vaccines include yellow fever, oral typhoid, varicella, MMR and BCG. For more detailed information, see the Canadian Immunization Guide, 7^th Edition 2006, Immunization of Immunocompromised Persons chapter for recommendations on the use of vaccines in individuals who are immunodeficient.

See also:
The Immunocompromised Traveler
Committee to Advise on Tropical Medicine and Travel (CATMAT) - April 1, 2007

Travellers who are pregnant

In general, live vaccines should be avoided in pregnancy, whereas inactivated (killed) vaccines are considered safe. For more detailed information, see the Canadian Immunization Guide, 7^th Edition 2006, chapter on Immunization in Pregnancy and Breast-Feeding as well as the individual vaccine chapters for recommendations for and contraindications to vaccines in pregnancy.

Malaria prophylaxis

There is no approved vaccine against malaria currently available.

Four components of malaria protection should be discussed with travellers: (a) the risk of acquiring malaria, (b) personal protective measures to prevent mosquito bites, (c) chemoprophylactic drugs (where appropriate) and (d) the need to seek early diagnosis and treatment of a febrile illness. Information concerning malaria, drug-resistant strains of Plasmodium and recommended drugs for prophylaxis and other preventive measures is regularly updated by CATMAT and published in the Canada Communicable Disease Report. Information is also available from local health departments, travel clinics and the Travel Medicine Program section on the PHAC Web site, http://www.travelhealth.gc.ca.

All travellers should be informed that malaria should be suspected if fever occurs during or after travel. Medical attention should be sought as soon as possible, and the traveller should request that a blood film be examined for malarial parasites.

See also:

Selected References

Centers for Disease Control and Prevention. Travelers' health: yellow book. Health infor-mation for international travel 2005-2006. Atlanta, GA: US Department of Health and Human Services, Public Health Service, 2005.

World Health Organization (WHO). International travel and health: vaccination requirements and health advice. Geneva: WHO, 2005.

Source: Canadian Immunization Guide, Seventh Edition, 2006