Objective: To determine the causes of low childhood immunization rates based on physicians' knowledge, attitudes, and self-reported practices concerning childhood immunization.
Design: A standardized telephone survey conducted by trained interviewers.
Setting: Primary care physicians across the United States.
Participants: A stratified random sample of office-based family physicians, pediatricians, and general practitioners younger than 65 years was selected from the American Medical Association master file list that includes nonmembers. Physicians seeing 5 or more patients per week younger than 6 years and having 50% or more primary care patients were eligible for study. Of 1769 eligible physicians who spoke directly with the interviewers, 70% (N = 1241) completed the questionnaire.
Interventions: The interview was designed to determine physicians' likelihood of recommending vaccination in common clinical scenarios and to probe reasons behind these decisions.
Results: Only 4% of physicians who thought the risk for side effects was increased by upper respiratory tract infection (URI) were likely to vaccinate a child with URI vs 55% of physicians who thought there would be no increased risk (P < .001). Eighty-three percent of those who thought the efficacy of measles, mumps, and rubella vaccine would not be affected by a URI recommended vaccination vs only 8% of physicians who thought efficacy would decrease (P < .001). Some respondents (11%) would not administer 3 injectable vaccines simultaneously based on beliefs about side effects, parental objections, and vaccine efficacy. Physicians' likelihood of vaccination also varied by type of visit: 47% were less likely to vaccinate a child with a URI in an acute care as opposed to a well-child setting.
Conclusion: Physicians' beliefs and practice policies materially influence their likelihood of recommending vaccinations.