High levels of vaccine hesitancy remain poorly understood during an epidemic. Using high-frequency data in France at departmental level and exploiting the Covid-19 vaccination campaign calendar, we observe that vaccination among the elderly influences vaccination among young adults. We then propose a simple epidemiological economic model with two partially vaccinated demographic groups – the young and the elderly – and two opinions on vaccination - “vaxxers” and “antivaxxers”. The utility to get vaccinated for the young depends on the vaccination behavior of the elderly, their opinion of the vaccine and the epidemic environment. Our results suggest that mutual interactions between individuals’ vaccination opinions and infection prevalence may lead to the emergence of oscillations and disease traps. The vaccination behavior of the elderly can be harnessed to promote vaccination.