The present invention provides an infection preventive agent which has no side effects, and which improves infectious diseases of infants, particularly newly born infants. The present invention is related to an infection preventive agent for infants which includes bifidobacteria.本發明提供一種改善乳兒、特別是出生後不久之乳兒之感染症,且無副作用之感染防禦劑。本發明係關於一種含有雙歧桿菌之適合乳兒之感染防禦劑。