This study uses longitudinal data to profile psychological characteristics of COVID-19 vaccine advocates, resisters, and converts. We conducted a two-wave longitudinal survey (Nwave1 = 3190, Nwave2 = 2193) in Hong Kong using stratified quota sampling. Among those who completed both survey waves, 458 (30.5%) were classified as vaccine advocates, 295 (19.7%) were vaccine resisters, and 621 (41.4%) were vaccine converts (who shifted away from hesitancy). Compared to advocates, resisters were more likely to be female, those without children, between 40 and 49 years old, democratic voters, and those with poor health. Highly educated individuals, non-democrats, and those in good health were more likely to convert from hesitancy to acceptance. Public trust in authorities and confidence in vaccine were the primary factors related to vaccine uptake. Those who were more confident in vaccine, those who increased in information consumption and risk perceptions towards the pandemic, and those who decreased in their trust of health professionals were more likely to convert. Our study complements the emerging global picture of COVID-19 vaccine acceptance by focusing on changes in vaccine hesitancy during the pandemic.