Who is motivated to accept a booster and annual dose? A dimensional and person-centered approach.

The transmissibility of new COVID-19 variants and decreasing efficacy of vaccines led authorities to recommend a booster and even an annual dose. However, people's willingness to accept new doses varied considerably. Using two independent longitudinal samples of 4596 (Mean age = 53.6) and 514 (Mean age = 55.9) vaccinated participants, we examined how people's (lack of) vaccination motivation for their first dose was associated with their intention to get a booster (Sample 1) and an annual dose (Sample 2) several months later (Aim 1). We also aimed to capture the impact of the motivational heterogeneity on these intentions by capitalizing on participants' different motivational profiles collected at baseline (Aim 2). Across both samples, autonomous motivation, controlled motivation, and distrust-based amotivation were uniquely related to, respectively, higher, lower, and even lower booster and annual dose intentions. Further, a two-step clustering procedure revealed five profiles, with the profiles characterized by higher autonomous motivation (i.e. Good Quality and High Quantity profiles) reporting the highest vaccination intentions and the profile characterized by the highest number of obstacles (i.e. Global Amotivated profile) yielding the lowest vaccination intentions. These results stress the critical need to support citizens' volitional endorsement of vaccination to harvest long-term benefits with respect to COVID-19.