Vaccination has been promoted to mitigate the spread of the coronavirus disease 2019 (COVID-19). Vaccination is expected to reduce the probability of and alleviate the seriousness of COVID-19 infection. Accordingly, this might significantly change an individuals subjective well-being and mental health. However, it is unknown how vaccinated people perceive the effectiveness of COVID-19 and how their subjective well-being and mental health change after vaccination. We thus observed the same individuals on a monthly basis from March 2020 to September 2021 in all parts of Japan. Then, large sample panel data (N=54,007) were independently constructed. Using the data, we compared the individuals perceptions of COVID-19, subjective well-being, and mental health before and after vaccination. Furthermore, we compared the effect of vaccination on the perceptions of COVID-19 and mental health for females and males. We used the fixed-effects model to control for individual time-invariant characteristics. The major findings were as follows: First, the vaccinated people perceived the probability of getting infected and the seriousness of COVID-19 to be lower than before vaccination. This was observed not only when we used the whole sample, but also when we used sub-samples. Second, using the whole sample, subjective well-being and mental health improved. The same results were also observed using the sub-sample of females, whereas the improvements were not observed using a sub-sample of males.