Freeze-dried Live Attenuated Hepatitis A Vaccine
Usage
- This vaccine is prescribed for active immunization against Hepatitis A infection. It is generally administered to individuals over one year of age.
- Pharmacological classification: Vaccine; specifically, a live attenuated viral vaccine.
- Mechanism of action: This vaccine introduces a weakened, live version of the Hepatitis A virus (HAV) into the body. This weakened virus is capable of stimulating an immune response without causing the disease itself. This immune response results in the production of antibodies specific to HAV, providing long-term protection against future infection.
Alternate Names
This type of vaccine is often referred to as live attenuated hepatitis A vaccine. Specific brand names vary by region and manufacturer, examples include Biovac-A and Mevac-A. There is not a combined freeze-dried live attenuated hepatitis A and B vaccine currently available; combination vaccines for Hepatitis A and B utilize inactivated hepatitis A virus.
How It Works
- Pharmacodynamics: The vaccine stimulates the body’s humoral immune response, leading to the production of anti-HAV antibodies. These antibodies neutralize the virus upon subsequent exposure, preventing infection.
- Pharmacokinetics:
- Absorption: Administered subcutaneously, the vaccine is slowly absorbed from the injection site.
- Metabolism: The attenuated virus replicates within the body, stimulating the immune response.
- Elimination: The virus and viral components are ultimately cleared by the immune system. The exact elimination pathways have not been fully characterized.
- Mode of action: The live attenuated HAV in the vaccine mimics a natural infection, triggering both B-cell and T-cell responses. B cells produce antibodies against HAV, while T cells recognize and eliminate infected cells.
- Receptor binding, enzyme inhibition, or neurotransmitter modulation: As a live attenuated virus vaccine, the primary mechanism relies on the immune response, not directly on interactions with specific cellular receptors, enzymes, or neurotransmitters.
Dosage
Standard Dosage
Adults: A single 0.5ml dose, administered subcutaneously over the deltoid muscle of the upper arm. A booster is typically not required.
Children (over 1 year): Same as adult dosing (single 0.5ml dose subcutaneously).
Special Cases:
- Elderly Patients: Standard dosing.
- Patients with Renal Impairment: Standard dosing.
- Patients with Hepatic Dysfunction: Standard dosing.
- Patients with Comorbid Conditions: Evaluate on a case-by-case basis, considering the specific condition and its potential impact on the immune response. Immunocompromised patients might not have an effective immune response.
Clinical Use Cases
This vaccine is intended for pre-exposure prophylaxis, not for use during acute medical situations such as intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations.
Dosage Adjustments
No specific dosage adjustments are routinely made. However, in immunocompromised individuals, the vaccine might not produce the expected immune response. This also applies to individuals receiving immunosuppressive therapy or those with malignancies.
Side Effects
Common Side Effects
- Pain and tenderness at the injection site.
- Transient, mild fever.
Rare but Serious Side Effects
- Allergic reactions (including anaphylaxis).
Long-Term Effects
Long-term side effects are rare.
Adverse Drug Reactions (ADR)
Severe allergic reactions require immediate intervention.
Contraindications
- Hypersensitivity to any vaccine component.
- Acute infectious disease or serious illness.
- Acute febrile illness with a temperature above 37.5°C.
- Immunodeficiency states.
- History of anaphylaxis or serious allergic reaction to vaccines.
Drug Interactions
- Immunosuppressants may decrease the vaccine’s effectiveness.
- Concurrent administration of immunoglobulin (IG) may interfere with the immune response to the vaccine. Administer IG at least three months before or after the vaccine.
Pregnancy and Breastfeeding
- Pregnancy: Use with caution if the benefits outweigh the risks. Limited data are available regarding its use during pregnancy.
- Breastfeeding: It is unknown whether the vaccine is excreted in breast milk. A decision must be made whether to discontinue breastfeeding or to discontinue/abstain from therapy taking into account the benefit of breastfeeding for the child and the benefit of therapy for the woman.
Drug Profile Summary
- Mechanism of Action: Stimulates immune response, producing anti-HAV antibodies.
- Side Effects: Pain at injection site, mild fever, rarely allergic reactions.
- Contraindications: Hypersensitivity, acute illness, immunodeficiency, history of anaphylaxis to vaccines.
- Drug Interactions: Immunosuppressants, immunoglobulins.
- Pregnancy & Breastfeeding: Caution advised.
- Dosage: Single 0.5ml dose subcutaneously.
- Monitoring Parameters: Observe for allergic reactions post-vaccination.
Popular Combinations
The live attenuated HepA vaccine is not usually given in combination with other vaccines in the same syringe; however, it can be administered concomitantly with other vaccines at separate injection sites.
Precautions
- Screen patients for allergies and contraindications before administration.
- Ensure epinephrine is available in case of anaphylaxis.
- Use a separate needle and syringe for each patient.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for the freeze-dried live attenuated hepatitis A vaccine?
A: A single 0.5 ml dose, administered subcutaneously.
Q2: Who should receive this vaccine?
A: Individuals over one year of age who are at risk of exposure to HAV.
A: No, it only protects against hepatitis A.
Q4: Are there any contraindications to receiving this vaccine?
A: Yes. Contraindications include hypersensitivity to vaccine components, acute illness, fever, immunodeficiency, and a history of vaccine-related anaphylaxis.
Q5: Can pregnant or breastfeeding women receive this vaccine?
A: It is not routinely recommended. Administer only if essential and the potential benefits outweigh the risks. Consult specialist guidance.
Q6: How long does protection from the vaccine last?
A: Protection is generally long-lasting, possibly lifelong, though some individuals may require a booster after many years.
Q7: What are the common side effects?
A: Common side effects include pain and tenderness at the injection site, and mild fever.
Q8: What should I do if a patient experiences a severe allergic reaction?
A: Administer epinephrine immediately and provide supportive care as needed.
Q9: Can this vaccine be given with other vaccines?
A: Yes, it can be given concomitantly with other vaccines, but at a separate injection site.
