[论文解读] Effect of the COVID-19 vaccine on preventive behaviors: Evidence from Japan

Eiji Yamamura, Youki Koska+2 more|arXiv (Cornell University)|Mar 15, 2022

COVID-19 Pandemic Impacts被引用 4

一句话总结

本研究利用日本18个月（2020年3月—2021年9月）内54,007名个体的月度面板数据，考察了接种2019冠状病毒病疫苗对预防行为的影响。出乎意料的是，总体而言，接种疫苗者并未减少戴口罩或洗手的频率，但40岁以下人群在接种后显著更可能增加外出活动，表明尽管卫生习惯未变，但其行为仍呈现年龄相关的转变。

ABSTRACT

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.

研究动机与目标

• 分析日本接种2019冠状病毒病疫苗后预防行为（戴口罩、洗手、居家）的变化。
• 将接种者与未接种者进行比较，以隔离疫苗对接种者行为的影响。
• 调查接种后行为变化的年龄差异，特别是40岁及以下与40岁以上人群之间的差异。
• 评估接种是否导致风险更高的行为，或在获得免疫力后仍持续采取保护性行为。
• 理解非正式社会规范在疫苗接种后维持预防行为中的作用。

提出的方法

• 2020年3月至2021年9月期间，每月收集日本54,007名个体的纵向面板数据。
• 使用固定效应模型控制个体特有的未观测特征和时间不变因素。
• 在同一个人群中比较接种前后的预防行为。
• 将接种者与未接种者进行比较，以估计因果效应。
• 按年龄进行子群分析，特别比较40岁及以下与40岁以上人群。
• 控制影响疫情期间行为的多种个体特征和外部因素。

实验结果

研究问题

• RQ1 在日本，接种2019冠状病毒病疫苗是否导致戴口罩和洗手等预防行为减少？
• RQ2 与未接种者相比，接种者随时间推移的预防行为如何变化？
• RQ3 接种后是否存在显著的年龄相关行为差异，特别是40岁以下与40岁以上人群之间？
• RQ4 非正式社会规范在多大程度上能维持疫苗接种后的预防行为，即使在接种后？
• RQ5 尽管持续采取预防措施，接种是否导致社交活动增加，如外出更频繁？

主要发现

• 总体而言，接种疫苗者在接种后并未显著减少居家频率、洗手频率或戴口罩频率，这与行为放松的预测相反。
• 在40岁及以下人群中，接种疫苗与外出可能性显著增加相关，表明其行为向更高程度的社会参与转变。
• 在40岁以上人群中，接种后预防行为无显著变化，与总体样本结果一致。
• 老年人群行为未发生变化，表明其对预防规范的遵守更强，或接种后仍感知到更高的风险。
• 结果表明，非正式社会规范可能在维持疫苗接种后预防行为方面发挥关键作用，尤其在行为非强制执行的群体中。
• 本研究未发现日本存在广泛‘疫苗接种导致自满’的证据，因为预防行为在人群中总体保持稳定。