 In a placebo controlled clinical trial, sixty six mothers will be randomly assigned to receive either 10,000 IU vitamin A or placebo capsules weekly from second trimester to 6 month postnatal period. At 26-28 weeks of gestation, all mothers will be vaccinated with inactivated, trivalent influenza virus vaccine. Maternal and cord blood will be collected for vitamin A and influenza virus specific IgG assessment. Colostrum and breast milk at 6-month will be collected for vitamin A and influenza virus specific secretory IgA assessment. Venous blood 2-3 ml will be obtained from all infants at the age of 6 months for vitamin A and influenza virus specific IgG assessment as well as infants nasal swab for influenza virus specific secretory IgA. 