**Core Concept**
Passive immunity is conferred to the newborn through maternal antibodies, which provide protection against infections such as varicella (chicken pox). In a healthy infant born to a mother with chicken pox, the risk of severe disease is minimal due to the presence of these maternal antibodies.

**Why the Correct Answer is Right**
In this scenario, the infant is afebrile and appears healthy, indicating that the maternal antibodies are likely sufficient to protect against varicella infection. The mother can continue to care for the infant without posing a significant risk of transmission. The maternal antibodies will provide the necessary protection, and the infant does not require specific treatment or isolation. The administration of acyclovir or VZIG is not necessary in this case, as the risk of severe disease is low.

**Why Each Wrong Option is Incorrect**
**Option B:** Hospitalization in an isolation ward is not necessary, as the risk of severe disease is minimal in a healthy infant with maternal antibodies.

**Option C:** Administering acyclovir, an antiviral medication, is not indicated in this case, as the risk of severe disease is low and the maternal antibodies provide adequate protection.

**Option D:** VZIG (varicella-zoster immunoglobulin) is not necessary, as the maternal antibodies will provide sufficient protection against varicella infection.

**Clinical Pearl / High-Yield Fact**
Newborns are protected against varicella infection by maternal antibodies, which are transferred during pregnancy. This protection typically lasts for 2-3 months after birth, providing a window of time during which the infant is at low risk for severe disease.

**✓ Correct Answer: A. Advise the mother to continue regular baby care**