Inactivated Hepatitis A Vaccine

Usage

• Medical Conditions: Inactivated hepatitis A vaccine is prescribed for the prevention of hepatitis A virus (HAV) infection. It is recommended for individuals at increased risk of exposure to HAV, including:

  • Travelers to regions with intermediate or high HAV endemicity
  • Individuals with chronic liver disease
  • Men who have sex with men
  • People who use injection or non-injection drugs
  • Individuals working with nonhuman primates
  • Individuals experiencing homelessness
  • Close contacts of internationally adopted children
  • Any person requesting vaccination

• Pharmacological Classification: Vaccine (viral, inactivated).

• Mechanism of Action: This vaccine stimulates an active immune response by exposing the body to inactivated (killed) HAV. This prompts the immune system to produce antibodies against HAV, providing long-term protection against future infection.

Alternate Names

• Inactivated HAV vaccine

• HepA vaccine

• Brand Names:

  • Havrix
  • Vaqta
  • Avaxim
  • Twinrix (combined Hepatitis A and B)
  • ViATIM (combined Hepatitis A and Typhoid)

How It Works

• Pharmacodynamics: The vaccine induces an immune response, leading to the production of anti-HAV antibodies. These antibodies neutralize the virus, preventing infection.

• Pharmacokinetics: The vaccine is administered intramuscularly (IM). The inactivated virus particles are taken up by antigen-presenting cells, leading to the activation of B cells and the production of specific anti-HAV antibodies.

• Mode of Action: The vaccine mimics natural HAV infection without causing illness. The inactivated virus particles stimulate both humoral and cellular immune responses. B-cells produce antibodies that bind to and neutralize HAV upon subsequent exposure. T-cells also contribute to long-lasting protection.

• Elimination Pathways: Not applicable for inactivated vaccines.

Dosage

Standard Dosage

Adults (≥19 years):

• Havrix, Vaqta, Avaxim: 1 mL IM, followed by a booster dose of 1 mL at 6-18 months after the primary dose. The specific interval (6-12 months for Havrix, 6-18 months for Vaqta) depends on the product.
• Twinrix: 1 mL IM at 0, 1, and 6 months.

Children (12 months - 18 years):

• Havrix, Vaqta, Avaxim: 0.5 mL IM, followed by a booster dose of 0.5 mL at 6-18 months after the primary dose. As with adults, the specific interval depends on the product.
• Twinrix Junior: 0.5 mL IM at 0, 1, and 6 months or two doses with a 6-month interval.
• Ambirix: 0.5 mL IM with two doses, 6 months apart.
• For infants 6-11 months traveling to endemic areas, a single dose of 0.5 mL can be administered, with revaccination using the two-dose schedule between 12 and 23 months of age. This initial dose does not count toward the standard two-dose series.

Special Cases:

• Elderly Patients: Same as adult dose.
• Patients with Renal Impairment: No dose adjustment necessary.
• Patients with Hepatic Dysfunction: No dose adjustment necessary for mild to moderate dysfunction. For severe dysfunction, consult specialist guidance.
• Patients with Comorbid Conditions: No specific dose adjustments unless there are contraindications related to a comorbid condition.

Clinical Use Cases The Inactivated Hepatitis A vaccine is primarily used for pre-exposure prophylaxis, not for the clinical situations listed below (intubation, surgical procedures, mechanical ventilation, etc.). For post-exposure prophylaxis, immunoglobulin should be considered.

Dosage Adjustments

• Immunocompromised individuals or those with chronic liver disease may require three doses at 0, 1, and 6 months.

Side Effects

Common Side Effects:

• Injection site reactions (soreness, redness, swelling, induration)
• Headache
• Fatigue
• Malaise
• Fever
• Nausea
• Loss of appetite

Rare but Serious Side Effects:

• Allergic reactions (including anaphylaxis)

Long-Term Effects: No known long-term adverse effects.

Adverse Drug Reactions (ADR):

• Anaphylaxis (rare)

Contraindications

• Hypersensitivity to any vaccine component (e.g., neomycin, latex found in some packaging components).

Drug Interactions

• Can be co-administered with other vaccines (including typhoid Vi polysaccharide and yellow fever vaccines) without significant interactions. However, it is recommended that different vaccines be administered at separate sites.
• Immunoglobulin can be administered concomitantly for post-exposure prophylaxis, but at a separate injection site.

Pregnancy and Breastfeeding

• Pregnancy: Data on use during pregnancy is limited, but the theoretical risk to the fetus is low because the vaccine is inactivated. Should be given during pregnancy only if clearly needed and after assessing risks and benefits.
• Breastfeeding: Can be administered to breastfeeding women. No known adverse effects on the infant.

Drug Profile Summary

• Mechanism of Action: Stimulates active immunity against HAV by inducing antibody production.
• Side Effects: Mostly mild injection site reactions and systemic symptoms. Rare allergic reactions.
• Contraindications: Hypersensitivity to any vaccine component.
• Drug Interactions: Can be safely co-administered with most vaccines.
• Pregnancy & Breastfeeding: Generally safe, but use with caution and only if clearly indicated.
• Dosage: Adults/Adolescents: Two doses of 1 mL / 0.5 mL at 0 and 6-18 months. Special populations may require three doses.
• Monitoring Parameters: None specific.

Popular Combinations

• Twinrix (Hepatitis A and B)
• ViATIM (Hepatitis A and Typhoid)

Precautions

• Postpone administration in individuals with severe febrile illness.

FAQs (Frequently Asked Questions)

Q1: What is the recommended dosage for Inactivated Hepatitis A Vaccine?

A: Adults and adolescents above 18 years: 1 mL IM, followed by a booster of 1 mL at 6-18 months (depending on the product). Children 12 months -18 years: 0.5 mL IM, followed by a booster of 0.5 mL at 6-18 months (depending on the product).

Q2: Can the vaccine be given during pregnancy?

A: While generally safe, it should only be given during pregnancy if clearly needed and after a thorough assessment of benefits and risks.

Q3: How long does protection last after vaccination?

A: Long-term protection (at least 25 years) is achieved after the two-dose series.

Q4: What are the most common side effects?

A: The most common side effects are mild and include injection site reactions (pain, soreness, redness), headache, fatigue, and low-grade fever.

Q5: Can this vaccine be given with other vaccines?

A: Yes, it can be administered concomitantly with most other vaccines but preferably at different injection sites.

Q6: Is there a vaccine for both Hepatitis A and B?

A: Yes, the Twinrix vaccine provides combined protection against hepatitis A and B.

Q7: What should I do if a dose is missed?

A: Contact a healthcare professional to reschedule the missed dose as soon as possible.

Q8: Who should receive the hepatitis A vaccine?

A: Individuals at increased risk of HAV infection, such as travelers to endemic areas, those with chronic liver disease, men who have sex with men, and people who use drugs. Anyone requesting the vaccine can also receive it.

Q9: How effective is the Hepatitis A vaccine?

A: It is highly effective (over 95%) in preventing HAV infection after completion of the two-dose series.