How long do babies carry their mother's immunity?

Passive immunity follows the baby for several months and is replaced by breastfeeding if you do breastfeed your baby. The immunity follows mummy whereby if mummy has had chicken pox then baby is protected from the virus. If baby is not breastfed then it is important to fight against infection as formula milk is unable to replicate the antibodies found in breastmilk. Good practices of hygiene and avoiding people or children who have higher changes of getting sick can help reduce the chances of your baby getting infected. http://www.babble.com/baby/newborn-immune-system/