Typhoid fever is an enteric febrile illness with symptoms that range from mild to potentially fatal. Among Canadians it is usually acquired during travel to typhoid endemic countries. The Committee to Advise on Tropical Medicine and Travel (CATMAT) assembled a typhoid working group to update recommendations on typhoid and international travel. This document is a summary of the new typhoid statement. Methods: Following a systematic review of the literature, typhoid vaccine recommendations were developed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology to evaluate data quality, benefits and harms, and values and preferences. The literature search focused on systematic reviews of typhoid vaccine efficacy and identified studies of disease burden, pathogenesis, risk factors and prevention. Other recommendations were based on a review of the retrieved literature and expert opinion. Results: Typhoid vaccine is moderately effective (~50%), well tolerated, with very low risk of serious adverse events. Studies of typhoid vaccine efficacy, morbidity or mortality among travellers were not found, although studies on populations in typhoid endemic countries were identified. Among travellers, destination of travel is the strongest and most consistent typhoid risk predictor; the highest risk was for travel to South Asia. Confidence in effect estimates for other potential risk factors was very low. Recommendations: CATMAT suggests that typhoid vaccine (Ty21a or Vi polysaccharide vaccine) be used for most Canadian travellers visiting South Asia and not used for most Canadian travellers visiting destinations other than South Asia. The recommendations are conditional, due to the moderate confidence in the effect estimate. For destinations other than South Asia, providers should discuss risks and vaccine benefits and harms with the traveller as well as recommend basic hygiene precautions.
M easles control is a high priority throughout Canada. Provincial and territorial immunization programs are in place to ensure high vaccination coverage among children. The effectiveness of the vaccine has generally been shown to be greater than 90%, and in recent years large areas in Canada and the United States either have remained measles free or have had only a few cases. Nevertheless, the occurrence of confirmed cases demonstrates the continuing presence of the measles virus. Sustained outbreaks have occurred, and a major resurgence of measles was documented in Canada and the United States in 1989.1,2 Primary and secondary vaccine failures have been documented. Primary failure is due to (a) vaccination in the presence of maternal antibody (i.e., in infants before 1 year of age), (b) improper handling or administration of the vaccine or (c) unknown causes. New stabilizers, introduced in 1980, and better attention to proper refrigeration likely have reduced the number of problems associated with improper handling. Secondary vaccine failure is due to waning immunity,3 but the proportion of people in whom this occurs appears to be small. If waning immunity were a significant problem one would expect the attack rate to increase steadily with age. This has not been observed.2 Even though vaccine coverage has been documented to be as high as 100% transmission of the measles virus can still occur. This may be because of transmission within the 2% to 10% of vaccinated people who have primary vaccine failure, occasional cases of secondary vaccine failure or poor immunization records and follow-up procedures. The following guidelines are intended to assist provincial and territorial epidemiologists and local health departments in developing strategies to control measles within their jurisdictions. The three main areas are immunization, surveillance (of cases and nonvaccinated people) and outbreak control.
T he general objectives of postmarketing surveillance of reactions to immunizing agents are (a) to identify reactions of infrequent occurrence that may be caused by such agents, (b) to develop estimates of the rates of occurrence of more serious reactions by type of vaccine, (c) to monitor for unusually high rates of adverse events, (d) to raise the awareness of health care providers of the risks of vaccines and the safety measures in administering them and (e) to identify areas that require further epidemiologic research. At the federal level surveillance for adverse events temporally associated with the administration of immunizing agents is the responsibility of the Disease Surveillance Division of the Bureau of Communicable Disease Epidemiology, Laboratory Centre for Disease Control, Ottawa. The main source of information has been a passive reporting system in which health care providers inform provincial or territorial authorities of events they think may have been due to the administration of immunizing agents. These reports, along with information from manufacturers and other agencies, are forwarded to the division. A computerized database has been established to include epidemiologic and medical information on reported events related to patients vaccinated since Jan. 1, 1987. To be eligible for inclusion the events had to meet previously published criteria' and not be attributable to any coexisting condition. Of the eligible reports some contained information on more than one immunizing agent or more than one adverse event for a given patient. Therefore, the number of reports (2519) was less than the number of associated agents (3531) and adverse events (3054). The number of adverse reactions to a specific agent represents the number of reports in which that agent was one of those given to the patient. The acceptance of a report into the database does not imply that there is a causal relation between the immunizing agent and the medical outcome or that the report was verified. The sensitivity, specificity and timeliness of the reporting system vary greatly by province and territory. Within a province these factors vary by the type of vaccine delivery system (public versus private). This article summarizes the reports received by Dec. 31, 1989, concerning reactions to immunizing agents given in 1988. Of the 4371 reports received 2519 (58%) met the eligibility criteria, as compared with 2113 (51%) of the 4146 reports received for 1987.
In Canada during 1990, a total of 2832 reports of adverse events temporally associated with the administration of immunizing agents were received by the Childhood Immunization Division of the Laboratory Centre for Disease Control. This paper summarizes the data collected, describes the surveillance system, and demonstrates that, with more than 12 000 000 doses of vaccines distributed during 1990, the incidence of adverse events reported is very low.
