how long is hep a vaccine good for
1 For healthy persons aged 12 monthsâ40 years, single-antigen Hepatitis A vaccine at the age-appropriate dose is preferred to IG because of the vaccineâs advantages, including long-term protection and ease of administration, as well as the equivalent efficacy of vaccine to IG.ersons who have recently been exposed to HAV and who have not been vaccinated previously should be administered a single dose of single-antigen Hepatitis A vaccine or IG (0.02 mL/kg) as soon as possible, within 2 weeks after exposure.