Immunizations for Travel Abroad


* Special Education Feature *

Travel to the tropics can be extremely rewarding and enjoyable as long as you do not bring any souvenirs home with you in the form of infectious diseases. The most frequent vaccine-preventable infection in travellers is Travellers’ Diarrhea, caused by an E. coli bacterium called ETEC (enterotoxigenic E. coli). Other vaccine-preventable infections that travellers should be aware of are influenza, Hepatitis A,, Typhoid Fever, Hepatitis B and, lastly, cholera (see Fig. 1).

Travellers’ Diarrhea
Diarrhea is the most frequent cause of illness in people who travel to developing countries, affecting up to 50% of travellers.

Impact studies on Travellers’ Diarrhea demonstrated that 40% of travellers had to modify daily activities, 33% were confined to bed, 1% were hospitalized and 2% had chronic diarrhea. Intuitively, one would expect that preventing enteric illnesses might be accomplished by cautious eating habits during travel; however, most studies demonstrated that travellers did not adhere to food and water precautions. A Swiss study showed that 98% of travellers made a food and/or beverage error within 72 hours of their arrival in the tropics. The most important determinant of risk is the travel destination and type of travel. The attack rate is higher in adventure travellers (backpackers) due to food preparation in unsanitary conditions as well as in those staying in luxury hotels or resorts (4 star or higher) due to increased opportunities for food contamination.

ETEC is the most common cause of Travellers’ Diarrhea and is responsible for up to one half of all diarrheal cases. Dukoral® is an oral vaccine licensed in Canada to help prevent Travellers’ Diarrhea caused by ETEC. Dukoral should be considered for travellers whose immune system is suppressed or for those who are frequently ill during travel, including people with chronic illnesses such as diabetes mellitus, chronic kidney disease and IBD. These people are at greater risk for serious consequences from Travellers’ Diarrhea. Immunocompromised persons, such as those with HIV, can receive Dukoral® but may not obtain the expected immune response. The good news is that the vaccine is taken orally in two doses, one week apart, and helps protect you against ETEC for 3 months.

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Influenza, a respiratory illness, is a frequent vaccine-preventable infection. It has been shown to occur in as many as 1.2% of travellers, with those visiting the Indian subcontinent most affected. Unlike its seasonal occurrence during the winter months in Canada, influenza occurs year round in the tropics.


Hepatitis A
Hepatitis A, a viral infection of the liver, is transmitted by contaminated water and food or through close contact with a recently infected individual. Globally, Hepatitis A is very common in tropical countries, across Asia and the former Soviet Union, and in popular Canadian winter getaway destinations. In a recent Quebec study, more than 40% of Hepatitis A cases in Quebec, for which risk-factor information was available, were contracted abroad, including in Mexico and the Caribbean.

New Canadians returning to their country of origin to visit friends and relatives (VFR) comprise a special travel population at high risk of acquiring infections, including Hepatitis A. The risk of Hepatitis A infection in young VFR travellers and their Canadian-born children is highly dependent on the residence location and duration of stay, age immigration year and history of jaundice. Often, those born in developing countries incorrectly assume that because they were exposed to many infectious diseases as a child, they are automatically immune to travel-related infections. This is not the case! For example, a recent study from India showed that 43% of individuals between the ages of 15 to 35 did not have the antibodies that protect against Hepatitis A.

Hepatitis A is generally characterized by jaundice, fever, fatigue and loss of appetite. However, 70% of children under the age of 6 do not display any signs of infection and can easily spread the infection among other children because of their lack of good hand hygiene. On the other hand, the severity of hepatitis A increases with age. About 25% of adults who acquire Hepatitis A end up being hospitalized.

Hepatitis A may be prevented by immunization. The three vaccines available are well tolerated and may provide long-term protection with two doses given 6-18 months apart. In general, the vaccines are effective. Even if you get only one dose of vaccine before you travel, you will still get short-term protection against Hepatitis A.*

Typhoid Fever
Typhoid fever is another infection transmitted by contaminated food and water. This serious disease is characterized by prolonged fever, abdominal pain and a rose-coloured rash. In severe cases it may be complicated by intestinal bleeding, bowel perforation and even death. In most industrialized countries, imported cases of Typhoid Fever are often in VFRs. Every VFR travelling to a developing country should be immunized against typhoid fever, regardless of the duration of travel. The vaccine should also be considered for frequent or long-stay travellers, and for those straying off the usual tourist routes — adventurous travellers and those wishing to try the local exotic food delicacies available.

The three typhoid vaccines available in Canada have been demonstrated to be well tolerated and, depending on the vaccine, can provide protection for 3-4 years. For those of you who would prefer fewer needles before travel, a Hepatitis A and Typhoid Fever combination vaccine is available (Vivaxim®). Vivaxim® is administered as a single dose before travel to people 16 years of age and older and is an appropriate choice for last minute travellers.

Hepatitis B
Hepatitis B poses a potential risk to people travelling to developing countries. It is reassuring to know that in Canada today most young travellers under the age of 27 have already been vaccinated for Hepatitis B in school or at birth through routine immunization programs. A combined Hepatitis A and B vaccine helps to provide prolonged protection, with three doses given over 6 months before travel. It is important that all travellers be protected against both Hepatitis A and Hepatitis B.

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Final Thoughts
When your trip involves more remote locations, you should consider seeking pre-travel advice from a travel clinic, if possible, 1 month prior to departure. Travel clinic locations and contact information can be found on the Public Health Agency of Canada website:

*Length of protection is not currently known. 100% protection cannot be guaranteed.