Psychological intervention of mass hysteria after immunized with pandemic influenza A (H1N1) vaccine

On 12 January 2010, the students in a primary school in Pingyang county, Wenzhou municipality were immunized with pandemic influenza A (H1N1) vaccine, a boy developed lethargy after the vaccination, then 3 girls developed similar symptoms. No clinical abnormity was found among them by examination. The diagnosis of mass hysteria (psychogenic reaction) was made. After the successful intervention by psychologist, no further worry arose among the students.