Immunization against infectious disease has probably saved more lives than any other public health intervention, apart from the provision of clean water 1. Vaccination programs are among the most effective public health initiatives undertaken, credited with eliminating small pox, virtually eliminating polio and substantially reducing the illness burden of infectious diseases such as diphtheria, pertussis, and measles 1. Vaccine technology has recently been profiled in the international press with emphasis on research aimed at new vaccines for Human Immunodeficiency Virus (HIV) and cancer 23. Terrorist threats have also focused attention on anthrax and smallpox vaccines as one means of public protection against bioterrorism 45.

While vaccines have provided benefits, the effectiveness of new and existing programs depends on the acceptance of the public, which is increasingly challenged by concerns about safety, particularly given possible findings linking multiple sclerosis and the hepatitis B vaccine, and allegations of linkage between autism and measles, mumps and rubella vaccines 67. While most public health officials and epidemiologists believe these fears to be unfounded, such fears undermine the effectiveness of vaccination programs. To provide an empirical basis for public education efforts, we undertook a national survey to better understand the public's acceptance of current and potential future vaccinations and to explore their attitudes and levels and types of knowledge.

Of the individuals contacted by telephone, 79.5% agreed to complete the survey (N = 1057). Demographic characteristics of the 1057 respondents are shown in Table 1. Year of birth was not provided by 30 respondents. The mean age of respondents was 44.78 years, with females (n = 513) slightly older (mean ± SD age = 45.9 ± 16.8 years) than males (n = 514, 43.72 ± 15.56, p < 0.05). More males (n = 321) were employed full-time than females (n = 213), while more females (n = 236) than males (n = 157) were unemployed (p < 0.001). Unemployed respondents were older (53.64 ± 16.2 years) than those working full-time (40.2 ± 10.15) or part-time (36.08 ± 14.91, p < 0.001).

The objective of this survey was to obtain a baseline measure of several key domains of attitudes and knowledge concerning vaccines in a population-based sample. Due to an absence of similar studies and the lack of comparative results, it is difficult to ascertain how representative our findings are and how modifiable or volatile attitudes might be over time. It is also not yet possible to assess the validity of results in predicting real behaviours, such as immunization refusal, because data on refusals is not currently readily available.

While most Canadians can be characterized as having positive opinions about vaccine effectiveness and research, there are some survey indications that might signal caution. On the question, 'The safeguards used in making vaccines are slack and ineffective', 40.4% of respondents indicated insufficient knowledge, 4.8% indicated uncertainty, while 10.5% agreed with the negatively worded statement. A positively worded question, 'The vaccines available are very carefully and consistently tested for safety', yielded somewhat similar results as 22.9% indicated insufficient knowledge, 4.5% indicated uncertainty while 5.3% indicated negative attitudes to the question. While it is debatable how much lay citizens might be expected to know, content-wise, about the safeguards implemented in producing vaccines, there is little question that positive indications of knowledge are desirable. The 40.4% response of insufficient knowledge may therefore be seen as one indication of where future education efforts might be directed.

In the context of this study, it would appear the attitudes subjects hold about vaccine safety and efficacy, and their self-perceived knowledge, generally, are associated with willingness to take either hypothetical vaccines currently in development (e.g. Hepatitis C, HIV-AIDS) or vaccines currently existing (Flu, Small Pox, Anthrax).

Most would be willing to take anthrax and smallpox vaccines, in view of the risks of bioterrorism. However, only 50% said they were actually taking the available influenza vaccine. Agreement to take vaccines that were currently unavailable on a widespread basis was higher – perhaps because these were for serious diseases, or because it is easier to endorse the acceptance of a vaccine that does not yet exist.

The result of this survey that might be an indication for most concern is the lack of knowledge about vaccines disclosed by Canadians. As many as 45% of respondents did not know enough to comment definitively about the safety of vaccines. Virtually, all substantive theories of behaviour change emphasize knowledge as a necessary factor in adoptive behaviour. Our results thus indicate a need for educational interventions, particularly given the real risks of bioterrorism. If we had to immunize on an emergency basis, either locally or regionally, a stronger base of public knowledge would be a valuable and perhaps highly important asset.

Although our survey indicated that 79.4% of subjects held positive views of vaccine efficacy, a majority of subjects (61.7%) were reluctant to dismiss anti-vaccine positions. This may reflect the public's potential for persuasion by pro- and anti-vaccine literature and argument. Perhaps because vaccine technology can appear counter-intuitive, i.e. a weakened pathogen or foreign protein is deliberately inserted in the body, it is an act of social trust to take a vaccine. One must trust the scientific discoveries underlying the vaccine and the production methods of the specific vaccination one receives. Furthermore, one must accept the 'tough love' of herd immunity – that the irreducible risks of vaccines mean some individuals experience the detriment of negative side effects (including fatality) for the beneficial protection of the great majority. In past studies that surveyed vaccinators and non-vaccinators 10, perceived dangerousness, doubts about efficacy, unwillingness to accept vaccine-mortality, beliefs that physicians overestimate disease risk and perceived disease susceptibility were the most significant factors predicting non-vaccination. Although the study, referred to above, used a highly selective sample, disproportionately selected from higher SES strata, it provided some validation of factors associated with vaccine refusal. The significant associations between our attitudinal and acceptability items can be interpreted as providing support for at least two (dangerousness and efficacy) of the predictive factors indicated in this other investigation.

In summary, our results indicate that despite a surprising lack of knowledge about vaccines, most Canadians are prepared to accept new vaccinations. Educational efforts on the part of public health officials may improve public receptivity. On the other hand, the lack of knowledge of vaccines may make Canadians susceptible to messages from anti-vaccination groups. An example of the potential impact of these groups can be seen in the UK where fears over Measles-Mumps-Rubella-induced autism have resulted in significant reductions in MMR coverage and consequent outbreaks of measles 28. If these impacts can occur under normal conditions and vaccination schedules, we may be more susceptible under conditions of heightened anxiety and emergency immunization.

PR, JI, NK, KW, LB, AR, RR, and MK participated in survey construction. AR performed survey translation. PR, JI, NK, KB, and MK completed data analysis. All authors participated in rough and final drafting.