**Core Concept**
HAV (Hepatitis A Virus) infection is a self-limiting illness, but it is highly contagious and can be prevented through vaccination or good hygiene practices. The virus is primarily spread through the fecal-oral route, making close contact with infected individuals or contaminated food and water a significant risk factor.

**Why the Correct Answer is Right**
To protect the 68-year-old father and the 6-month-old son from HAV infection, vaccination is the most effective measure. HAV vaccine is recommended for all individuals at risk of exposure, including close contacts of infected individuals. The vaccine is highly effective in preventing HAV infection and can be administered to individuals of all ages, including children as young as 6 months old. The 68-year-old father can receive a single dose of inactivated HAV vaccine, while the 6-month-old son can receive a series of two doses, with the second dose administered 6-12 months after the first dose.

**Why Each Wrong Option is Incorrect**
**Option A:** Administering immunoglobulin (IVIG) to the father and son is not the primary method of prevention for HAV infection. While IVIG can provide temporary protection against HAV, it is not a substitute for vaccination and has a shorter duration of action.

**Option B:** Isolating the father and son from the infected individual is a good hygiene practice, but it is not sufficient to prevent HAV infection. The virus can be present in the environment for an extended period, making it difficult to prevent exposure through contaminated food and water.

**Option C:** Stating that no action is needed is incorrect, as the father and son are at risk of exposure to HAV and can benefit from vaccination.

**Clinical Pearl / High-Yield Fact**
The HAV vaccine is a critical component of prevention strategies for individuals at risk of exposure to HAV, including close contacts of infected individuals, travelers to endemic areas, and individuals with underlying liver disease.

**Correct Answer:** C. Vaccination with inactivated HAV vaccine should be administered to the father and son to protect them from HAV infection.