William K.Hallman, from Rutgers Uniersity in New Brunswick, New Jersey, examined how subjectie and objectie risk influence accination behaiors in a random sample of 300 Americans.

• Hallman博士（新泽西洲洛特格斯大学纽布郎斯威克分校）研究了3000名美国人中影响接种疫苗行为的主观和客观因素。