Which of the following is the recommended schedule for administration of the hepatitis A vaccine?

The recommended schedule for the hepatitis A vaccine is indeed two doses administered at least 6 months apart. The primary vaccination series consists of two doses: the first dose can be given at any time, and the second dose is recommended to be administered 6 to 18 months later, but not less than 6 months apart to ensure optimal immune response and long-lasting protection.

This extended interval between doses allows the body to generate a robust immune response to the initial dose, thereby enhancing the effectiveness of the vaccination. The six-month interval is critical for achieving the desired immunologic memory, which is essential for long-term protection against hepatitis A virus infection.

The other options provide dosing schedules that either do not meet the minimal required time frames or intervals that are shorter than recommended, which could compromise the vaccine efficacy.