 Catechins are the major components of tea flavonoids and are reported to possess physiological activities such as antiviral effects. Recent in-vitro experimental studies have revealed that tea catechin extracts possess the effects on the prevention of influenza infection. However, a limited number of studies have been conducted on the clinical effects. Based on these backgrounds, we designed a prospective randomized controlled study to evaluate the effects of tea catechin extracts containing mask on the prevention of influenza infection. 