In most countries, vaccine uptake is a voluntary decision. If people experience threats to this freedom, for example, by pro-vaccination media campaigns or government pressure, psychological reactance may be induced. To regain freedom, the opposite behaviour (vaccine refusal) may become more attractive, forming a vaccination barrier. It remains unclear how state reactance fluctuates and how it relates to vaccination intention versus behaviour. Therefore, this pre-registered longitudinal study aimed to gain insight in the changes in state reactance during a COVID-19 vaccination programme and its relationship with vaccine uptake. A representative sample of Dutch adults under 60 completed questionnaires before being eligible for vaccination, shortly before they were invited for vaccination, and after the opportunity for vaccination. Data were analysed using regression analyses (N = 1411). Reactance did not change as hypothesised, but remained stable over time. As hypothesised, reactance predicted lower subsequent vaccination intention. Controlling for intentions, however, reactance did not predict vaccine uptake. Furthermore, reactance predicted lower decision confidence about vaccination, except for people who strongly opposed vaccination. Reactance has a sustained role in anticipation of a vaccination decision. Although reactance seems to affect the process towards the decision, this does not determine the final choice.