At what stage of pregnancy should the Tdap vaccine be administered to ensure protection for the newborn?

The Tdap vaccine should be administered during the 27-36 weeks of gestation because this timing helps maximize the transfer of maternal antibodies to the newborn. Administering the vaccine in this window ensures that the mother has enough time to develop an immune response and produce antibodies, which can be passed through the placenta to the fetus. This is critical for the newborn's protection against pertussis, especially since young infants are at high risk for severe complications from whooping cough.

While vaccination during the first or second trimester is beneficial for other health reasons, the optimal period for Tdap is specifically later in the pregnancy. Giving the vaccine postpartum does not provide protection to the newborn before birth, as maternal antibodies would not be transferred in time. Therefore, the recommended timing focuses on maximizing the immunological benefits for the infant right from birth.