Answer:
Case study 2:
The children who have previously suffered from chicken pox are immune to the virus because their immune systems have developed antibodies against it. When exposed to the virus again, their immune system recognizes it and quickly produces more antibodies, preventing the infection from taking hold. This is known as acquired immunity.
Case study 3:
When a baby is born, it receives important nutrients and immune factors from breast milk that provide protection against infectious diseases. If breastfeeding is delayed for more than 1 hour after birth, there is a greater chance that the baby may become sick or experience complications. The baby's immune system is not fully developed at birth, so early breastfeeding provides important support and protection. Delayed initiation of breastfeeding may also indicate other difficulties during delivery, such as prematurity, low birth weight, or maternal health problems, which can increase the risk of neonatal mortality. Therefore, the systematic review found that delayed breastfeeding initiation 2-23 hours after birth was associated with a higher risk of mortality compared to breastfeeding initiation within 1 hour after birth.