How Long Does the Hepatitis A Vaccine Last?
Hepatitis A, also known as Hepatitis A Virus (HAV), is a contagious liver infection caused by the hepatitis A virus. It primarily affects the liver and can impact individuals of all age groups, though children and teenagers are most commonly affected. Due to its prevalence among younger populations, it is highly recommended that infants receive the hepatitis A vaccine to prevent infection. A common question many parents and individuals have is: how long does the hepatitis A vaccine provide protection?
Types of Hepatitis A Vaccines and Their Effectiveness
Currently, there are two main types of hepatitis A vaccines available: inactivated vaccines and live attenuated vaccines. The inactivated vaccine contains purified, killed virus particles, while the live attenuated vaccine uses a weakened form of the virus to stimulate immunity. Live attenuated vaccines come in two forms — liquid (water needle) and freeze-dried. The liquid version is more affordable and typically provides protection for over five years, although it may be less stable during storage and transport. In recent years, freeze-dried live vaccines have been developed to address this issue, offering improved stability.
On the other hand, the inactivated hepatitis A vaccine offers a much longer duration of protection — often lasting over 20 years. Because the virus is completely inactivated, there is no risk of the vaccine reverting to a virulent form. This makes the inactivated vaccine a safer option, and it is widely used in countries around the world.
Best Time to Get the Hepatitis A Vaccine
The inactivated hepatitis A vaccine is one of the vaccines recommended by the World Health Organization (WHO). Children as young as 1 year old can receive the vaccine, as their immune systems are still developing and they are more vulnerable to infection. Research shows that approximately 8 weeks after vaccination, the body develops a strong immune response with high antibody levels, offering robust protection against the virus.
Vaccination Schedule for Hepatitis A
- Primary vaccination: Recommended for individuals aged 1 year and older who are susceptible to the virus.
- Booster dose: A second dose can be administered 6 months after the initial shot for long-term immunity.
- For those previously vaccinated with a live attenuated vaccine: Regardless of the time since the last dose, a booster can be given to enhance immunity.
Long-Term Immunity with Hepatitis A Vaccination
Recent studies on vaccinated populations have shown that when the live attenuated hepatitis A vaccine is administered in a two-dose schedule — with intervals of 1 month, 3 months, 6 months, or even 12 months — the anti-HAV antibody positivity rate reaches 100%, with antibody levels exceeding 1000 mIU/ml. This indicates that receiving two doses of the live attenuated vaccine can provide lifelong immunity against hepatitis A.