The aim of this study was to evaluate the efficacy of colostrum (ARD Colostrum) in association with the immunomodulator Bifivir in the prevention of flu episodes compared with anti-flu vaccination. The registry groups included no prevention, vaccination, vaccination+immunomodulators, and immunomodulators only. Groups were comparable for age and sex distribution. In the group without prevention there were 8 major episodes and 12 minor episodes out of 34 subjects (8-12/34); in the vaccination group the respective figures were 8-13/38; in the group treated with a combination of vaccination and immunomodulators (ARD Colostrum + Bifivir) the figures were 4-9/33; and in the group treated with immunomodulators only there were 11 viral episodes (3-8) in 36 subjects. The episodes in the vaccination+immunomodulators and immunomodulators only groups were significantly lower compared with the other two groups (P<0.05). The number of episodes registered with the immunnomodulators was significantly lower than those observed in patients using vaccination or no prevention (P<0.05). The number of days of disease was higher in untreated controls compared to the groups treated with immunomodulators (P<0.05) and 2 times higher in the vaccination group compared to the same groups (P<0.05). The average relative costs were significantly lower (2.3 times) in the immunomodulators groups in comparison with the other groups (P<0.05). No problems concerning tolerability or side effects were observed during the study. Compliance was very good. In conclusion, the administration of immunomodulators is very cost effective and appears to be more effective than vaccination to prevent flu.