Effect of the COVID-19 vaccine on preventive behaviors: Evidence from Japan

Vaccination against the coronavirus disease 2019 (COVID-19) is a key measure to reduce the probability of getting infected with the disease. Accordingly, this might significantly change an individuals perception and decision-making in daily life. For instance, it is predicted that with widespread vaccination, individuals will exhibit less rigid preventive behaviors, such as staying at home, frequently washing hands, and wearing a mask. We observed the same individuals on a monthly basis for 18 months, from March 2020 (the early stage of the COVID-19 pandemic) to September 2021, in Japan to independently construct large sample panel data (N=54,007). Using the data, we compare the individuals preventive behaviors before and after they got vaccinated; additionally, we compare their behaviors with those individuals who did not get vaccinated. Furthermore, we compare the effect of vaccination on the individuals less than or equal to 40 years of age with those greater than 40 years old. The major findings determined after controlling for individual characteristics using the fixed effects model and various factors are as follows. First, as opposed to the prediction, based on the whole sample, the vaccinated people were observed to stay at home and did not change their habits of frequently washing hands and wearing a mask. Second, using the sub-sample of individuals aged equal to or below 40, we find that the vaccinated people are more likely to go out. Third, the results obtained using a sample comprising people aged over 40 are similar to those obtained using the whole sample. Preventive behaviors are affecting oneself and generating externalities on others during this pandemic. Informal social norms motivate people to increase or maintain preventive behaviors even after being vaccinated in societies where such behaviors are not enforced.