•Trust in the CDC is one of the most important predictors of flu vaccination.•Trust matters 45% more when vaccination is offered in a supportive environment.•This includes include insurance with no co-pay and HCPs who discuss the vaccine.•Trust is a necessary condition but has to be combined with structural support. To understand whether health insurance coverage of vaccine costs and discussing vaccination with a healthcare provider are necessary for trust in CDC (Centers for Disease Control) to increase the uptake of the vaccine. A nationally representative sample of 2,549 adults from the United States answered questions about trust in CDC, insurance coverage, interactions with healthcare providers, and risk perceptions, and then provided longitudinal reports of actual vaccination against influenza during the course of the 2018–19 flu season. Trust in CDC as a source of information on vaccines was a strong precursor of vaccination. According to multilevel regressions, however, this effect was localized to respondents who had insurance coverage or whose providers discussed the vaccine with them. Further, the effect of trust was even stronger when both insurance coverage and healthcare provider discussions were present. Environmental factors supportive of vaccination increased the positive influence of trust in CDC on vaccine uptake by almost 50 percent. Insurance companies and healthcare providers can promote vaccination by covering the costs of vaccination and discussing vaccines in personalized conversations with patients.