An important influence on parents' decisions about pediatric vaccination (children under 6 years of age) is the attitude of their health care providers, including complementary and alternative medicine (CAM) providers. Very limited qualitative research exists, however, on how attitudes towards vaccination develop among healthcare professionals in-training. We explored perspective development among three groups of students: medical, chiropractic, and naturopathic. We conducted focus group sessions with participants from each year of study at three different healthcare training programs in Ontario, Canada. Semi-structured and open-ended questions were used to elicit dynamic interaction among participants and explore how they constructed their attitudes toward vaccination at the beginning and part way through their professional training. Analyses of verbatim transcripts of audiotaped interviews were conducted both inductively and deductively using questions structured by existing literature on learning, professional socialization and interprofessional relations. We found five major themes and each theme was illustrated with representative quotes. Numerous unexpected insights emerged within these themes, including students' general open-mindedness towards pediatric vaccination at the beginning of their training; the powerful influence of both formal education and informal socialization; uncritical acceptance of the vaccination views of senior or respected professionals; students' preference for multiple perspectives rather than one-sided, didactic instruction; the absence of explicit socio-cultural tensions among professions; and how divergences among professional students' perspectives result from differing emphases with respect to lifestyle, individual choice, public health and epidemiological factors--rather than disagreement concerning the biomedical evidence. This last finding implies that their different perspectives on pediatric vaccination may be complementary rather than irreconcilable. Our findings should be considered by developers of professional and interprofessional educational curricula and public health officials formulating policy on pediatric vaccination.