Hepatitis A Virus Strain Hm175 Antigen (formaldehyde Inactivated)

For adults aged 19 years and older, the standard dosing regimen for Hepatitis A Virus Strain Hm175 Antigen (formaldehyde Inactivated) consists of a two-dose series. The standard dose is 1440 ELISA Units (EL.U.) administered in a 1.0 mL volume.

• Primary Dose: 1440 EL.U. (1.0 mL) at month 0.
• Booster Dose: 1440 EL.U. (1.0 mL) administered 6 to 12 months after the primary dose.

This two-dose schedule is designed to ensure long-term persistence of anti-HAV antibodies. If the booster dose is delayed, healthcare providers typically recommend administering it as soon as possible to complete the series, rather than restarting the series.

The pediatric dosing schedule is approved for children and adolescents aged 12 months through 18 years. The concentration is lower than the adult dose.

• Standard Pediatric Dose: 720 EL.U. administered in a 0.5 mL volume.
• Primary Dose: 720 EL.U. (0.5 mL) at month 0.
• Booster Dose: 720 EL.U. (0.5 mL) administered 6 to 12 months after the primary dose.

For children, the vaccine is part of the routine immunization schedule recommended by the Advisory Committee on Immunization Practices (ACIP).

Renal Impairment

No dosage adjustments are typically required for patients with renal impairment or those undergoing hemodialysis. However, the immune response in these patients may be less robust than in healthy individuals, and post-vaccination serological testing may be considered by a healthcare provider to confirm protection.

Hepatic Impairment

No dosage adjustments are required for patients with hepatic impairment. In fact, patients with chronic liver disease are a priority group for this vaccine because they are at higher risk of complications from a Hepatitis A infection.

Elderly Patients

Clinical trials have shown that while the vaccine is safe in elderly patients, the peak antibody levels may be lower and the time to achieve seroconversion may be longer compared to younger adults. No specific dose adjustment is recommended, but the importance of the second booster dose is emphasized in this population.

This vaccine must be administered by a healthcare professional via intramuscular (IM) injection. The preferred site for adults and older children is the deltoid muscle (upper arm). For infants (12-23 months), the anterolateral aspect of the thigh is the preferred site.

• Preparation: The vial or syringe should be shaken well before use to maintain a uniform, turbid white suspension. If the contents appear discolored or contain large particulates after shaking, the vaccine should not be used.
• Administration: It should NOT be administered intravenously, intradermally, or subcutaneously, as these routes have not been studied and may result in a suboptimal immune response.
• Storage: The vaccine must be stored refrigerated between 2°C and 8°C (36°F to 46°F). It must NEVER be frozen. If the vaccine has been frozen, it loses its potency and must be discarded.

If you miss the scheduled window for your second (booster) dose, contact your healthcare provider immediately. You do not need to restart the series if the second dose is delayed; however, you may not have full, long-term protection until the second dose is completed. The booster can be given even if several years have passed since the first dose, according to CDC guidelines.

Because this medication is administered by healthcare professionals in fixed single-dose units, an overdose is highly unlikely. In the event of an accidental administration of a larger-than-intended volume, the patient should be monitored for increased severity of local injection site reactions or systemic side effects like headache and fatigue. There is no specific 'antidote' for a vaccine overdose; treatment is supportive.

> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose or skip the booster without medical guidance.

Side effects from the Hepatitis A Virus Strain Hm175 Antigen are generally mild and self-limiting, typically resolving within 24 to 48 hours. The most common reactions are local to the injection site, reflecting the body's immediate inflammatory response to the antigen and the aluminum adjuvant.

• Injection Site Soreness: This is the most frequently reported side effect, occurring in over 50% of adults. It feels like a dull ache in the deltoid muscle, similar to the soreness felt after a vigorous workout.
• Headache: Reported by approximately 14% of vaccine recipients. It is usually mild and responds well to over-the-counter pain relievers (as recommended by a doctor).
• Fatigue: A general feeling of tiredness or low energy as the immune system works to process the antigen.
• Redness and Swelling: Mild inflammation at the site of the needle entry.

• Fever: A low-grade fever (usually under 101°F) may occur, particularly in children.
• Nausea and Loss of Appetite: Some individuals may experience mild gastrointestinal upset or a temporary decrease in desire to eat.
• Malaise: A general 'unwell' feeling or 'flu-like' symptoms without the full respiratory components of the flu.
• Induration: A hardening of the tissue at the injection site.

• Syncope (Fainting): This can occur after any injection, particularly in adolescents, as a vasovagal response to the needle rather than the vaccine itself.
• Lymphadenopathy: Swelling of the lymph nodes, usually in the armpit (axilla) on the side where the injection was given.
• Dizziness and Vertigo: A temporary feeling of spinning or lightheadedness.
• Rash or Urticaria (Hives): Mild allergic skin reactions.

While extremely rare, serious adverse events can occur. If you experience any of the following, contact emergency services or your doctor immediately:

• Anaphylaxis: A severe allergic reaction characterized by difficulty breathing, swelling of the face or throat, rapid heartbeat, and a sharp drop in blood pressure.
• Angioedema: Deep swelling of the skin, often around the eyes or lips.
• Neurological Symptoms: Rare reports of Guillain-Barré Syndrome (GBS) have been noted post-marketing, though a definitive causal link to the Hepatitis A vaccine is not established. Symptoms include tingling or weakness in the legs that spreads to the upper body.
• High Fever: A temperature exceeding 103°F or a fever that does not respond to medication.

> Warning: Stop taking Hepatitis A Virus Strain Hm175 Antigen (formaldehyde Inactivated) and call your doctor immediately if you experience any signs of a severe allergic reaction.

There are no known long-term negative side effects associated with the Hepatitis A Virus Strain Hm175 Antigen. The 'long-term effect' intended by the vaccine is the persistence of anti-HAV antibodies. Extensive post-marketing surveillance over three decades has confirmed that the vaccine does not increase the risk of chronic diseases or autoimmune conditions.

No FDA black box warnings have been issued for Hepatitis A Virus Strain Hm175 Antigen (formaldehyde Inactivated). It is considered one of the safest vaccines in the standard immunization schedule.

Report any unusual symptoms or side effects to your healthcare provider. In the United States, healthcare providers are required to report certain adverse events to the Vaccine Adverse Event Reporting System (VAERS).

Hepatitis A Virus Strain Hm175 Antigen (formaldehyde Inactivated) is intended for the prevention of Hepatitis A, not for the treatment of an active infection. It will not protect against Hepatitis B, Hepatitis C, Hepatitis E, or other pathogens that infect the liver. It is also important to note that the vaccine may not provide 100% protection in all individuals, particularly those who are immunocompromised.

There are no FDA black box warnings for Hepatitis A Virus Strain Hm175 Antigen (formaldehyde Inactivated).

Allergic Reactions / Anaphylaxis Risk

As with all injectable vaccines, appropriate medical treatment and supervision must be available to manage possible anaphylactic reactions following administration. Patients with a known severe allergy to neomycin (an antibiotic used in the manufacturing process) or formaldehyde should inform their doctor, as trace amounts may remain in the final product.

Acute Febrile Illness

Vaccination should typically be delayed in individuals suffering from an acute, severe febrile illness (high fever). A minor illness, such as a mild upper respiratory infection or 'cold' with low-grade fever, is generally not a reason to delay vaccination, but the final decision rests with the healthcare provider.

Latex Sensitivity

Some formulations of the vaccine are packaged in vials or syringes that may contain dry natural rubber (latex) in the plunger stoppers or needle caps. Individuals with severe latex allergies should consult their doctor to ensure a latex-free version is used.

Altered Immunocompetence

In patients receiving immunosuppressive therapy (such as chemotherapy or high-dose corticosteroids) or those with immunodeficiency syndromes (like HIV/AIDS), the expected immune response may not be achieved. While the vaccine is safe (because it is inactivated and cannot cause infection), it may be less effective.

Routine lab testing is not required before or after vaccination for most people. However, in specific high-risk scenarios (e.g., healthcare workers at high risk of exposure or immunocompromised patients), a doctor may order an anti-HAV antibody titer test 1 to 2 months after the second dose to confirm seroconversion.

There is no evidence to suggest that this vaccine interferes with the ability to drive or operate heavy machinery. However, if a patient experiences dizziness or syncope (fainting) immediately following the injection, they should wait until symptoms resolve before driving.

There are no known direct interactions between alcohol and the Hepatitis A vaccine. However, chronic heavy alcohol use can weaken the immune system and may potentially reduce the effectiveness of the vaccine's immune response. Furthermore, alcohol can irritate the liver, which is the organ the vaccine is designed to protect from viral attack.

'Discontinuation' in the context of a vaccine refers to not completing the two-dose series. While the first dose provides significant short-term protection, failing to receive the booster dose may result in the loss of immunity over time. There are no withdrawal syndromes associated with stopping the vaccine series.

> Important: Discuss all your medical conditions and any history of vaccine reactions with your healthcare provider before starting Hepatitis A Virus Strain Hm175 Antigen (formaldehyde Inactivated).

There are no specific drugs that are absolutely contraindicated for use with Hepatitis A Virus Strain Hm175 Antigen. However, the timing of administration relative to other treatments is critical for efficacy.

Immunosuppressive Therapies

Drugs that suppress the immune system can significantly reduce the body's ability to respond to the HM175 antigen. These include:

• Chemotherapy: Cytotoxic agents used for cancer treatment.
• Systemic Corticosteroids: High-dose prednisone or similar medications taken for more than two weeks.
• Biologics: TNF inhibitors (e.g., adalimumab, etanercept) used for autoimmune diseases.
• Radiation Therapy: Particularly if it involves large areas of bone marrow.

Clinical Consequence: The vaccine will not be harmful, but it may fail to produce enough antibodies to protect the patient from Hepatitis A.

Management: If possible, vaccination should be completed at least two weeks before starting immunosuppressive therapy or delayed until the therapy is finished.

Immunoglobulins (IG)

If a patient has recently received immune globulin for post-exposure prophylaxis or as a treatment for another condition, it may interfere with the 'take' of the vaccine.

Mechanism: The passive antibodies in the IG may bind to the vaccine antigen before the patient's own immune system can recognize it.

Management: The vaccine can be given at the same time as IG, but they must be administered at different injection sites using separate syringes. This is common for rapid protection in travelers.

There are no known interactions between Hepatitis A Virus Strain Hm175 Antigen and food, including grapefruit, dairy, or high-fat meals. The vaccine's efficacy is not affected by dietary intake.

There are no documented interactions with common herbal supplements like St. John’s Wort, ginkgo biloba, or valerian root. However, supplements that claim to 'boost' or 'alter' the immune system should be discussed with a doctor, as their effect on vaccine-induced immunogenicity is unknown.

• Anti-HAV Serology: Following vaccination, a patient will test positive for anti-HAV IgG antibodies. This is a sign of immunity, not active infection. To diagnose an active infection, doctors look for anti-HAV IgM antibodies, which are not typically produced in significant amounts by the inactivated vaccine.
• Liver Function Tests (LFTs): The vaccine does not typically cause elevations in ALT, AST, or bilirubin. If these are elevated post-vaccination, a healthcare provider should look for other causes.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, especially those that affect your immune system.

There are very few absolute contraindications for the Hepatitis A Virus Strain Hm175 Antigen, as it is an inactivated (non-live) product. However, the following apply:

1. 1Severe Allergic Reaction to a Previous Dose: If a patient experienced anaphylaxis or another life-threatening reaction after the first dose of a Hepatitis A vaccine, they must NEVER receive a second dose of that specific formulation.
2. 2Hypersensitivity to Vaccine Components: Individuals with a documented, severe (anaphylactic) allergy to any component of the vaccine, including:

• Aluminum Hydroxide: Used as an adjuvant.
• Neomycin: Trace amounts of this antibiotic may be present.
• Formaldehyde: Used to inactivate the virus.
• 2-Phenoxyethanol: Used as a preservative in some formulations.

Mechanism: Re-exposure to these allergens can trigger a systemic IgE-mediated response leading to anaphylactic shock.

These are conditions where the healthcare provider will perform a risk-benefit analysis before proceeding:

• Moderate to Severe Acute Illness: As mentioned in the warnings, vaccination is usually deferred until the patient recovers to avoid diagnostic confusion between vaccine side effects and the underlying illness.
• Pregnancy: While not a contraindication, the lack of extensive clinical trial data in pregnant women means it is usually reserved for those at high risk of exposure.
• Bleeding Disorders: In patients with hemophilia or thrombocytopenia (low platelets), intramuscular injections can cause significant bruising or hematomas. The vaccine may be administered if the benefit outweighs the risk, often using a fine-gauge needle and applying firm pressure for several minutes.

Patients who are allergic to other inactivated viral vaccines (like the inactivated polio vaccine or the Hepatitis B vaccine) should be screened carefully, as they may share similar preservatives or manufacturing residuals (like neomycin).

> Important: Your healthcare provider will evaluate your complete medical history and previous vaccine reactions before administering Hepatitis A Virus Strain Hm175 Antigen (formaldehyde Inactivated).

Hepatitis A Virus Strain Hm175 Antigen is classified as Pregnancy Category C by the older FDA system (meaning animal studies show an effect or there are no human studies). However, because the vaccine is inactivated, it is generally considered to pose a low risk to the fetus. The CDC states that the safety of Hepatitis A vaccine during pregnancy has not been determined; however, because it is produced from inactivated virus, the theoretical risk to the developing fetus is expected to be low. Vaccination should be considered for pregnant women who are at high risk for infection (e.g., travelers to endemic areas or those with chronic liver disease).

It is not known whether Hepatitis A Virus Strain Hm175 Antigen is excreted in human milk. However, since the vaccine is inactivated and not a live virus, it is not expected to pose a risk to the nursing infant. The benefits of maternal immunization and the protection it provides to the mother usually outweigh any theoretical risks to the infant. No special precautions are required for breastfeeding mothers.

The vaccine is FDA-approved and highly recommended for children starting at 12 months of age. The pediatric dose (720 EL.U.) is specifically formulated for this age group. Clinical trials have demonstrated that the vaccine is highly immunogenic in children, with seroconversion rates approaching 100% after the two-dose series. It is not currently approved for infants under 12 months of age, as maternal antibodies may interfere with the infant's immune response to the vaccine.

In clinical studies, individuals over age 65 responded to the vaccine, but their antibody levels were often lower than those seen in younger adults. This is attributed to 'immunosenescence'—the natural aging of the immune system. Despite this, the vaccine remains effective and is recommended for older adults who have risk factors for HAV. There is no increased risk of adverse events in the elderly compared to younger populations.

Patients with renal failure or those on hemodialysis can safely receive the vaccine. However, their immune response may be suboptimal. Healthcare providers may consider testing for anti-HAV antibodies after the series is complete to ensure the patient has achieved protective levels. No dose adjustment is necessary.

Patients with chronic liver disease (including cirrhosis, Hepatitis B, or Hepatitis C) are at significantly increased risk for severe complications if they contract Hepatitis A. Therefore, this population is a primary target for vaccination. The vaccine is safe in these patients, and no dose adjustments are required. It should be administered as early as possible in the course of their liver disease for the best immune response.

> Important: Special populations require individualized medical assessment to determine the optimal timing for vaccination.

Hepatitis A Virus Strain Hm175 Antigen (formaldehyde Inactivated) works by inducing active immunity through the production of specific IgG antibodies. The HM175 strain contains the essential epitopes (binding sites) of the Hepatitis A virus. When introduced into the muscle, the antigen is recognized by B-cells. These B-cells, with the help of T-helper cells, differentiate into plasma cells that secrete anti-HAV antibodies. These antibodies remain in the circulation and can neutralize live HAV by binding to the viral capsid and preventing it from entering hepatic cells (liver cells).

The pharmacodynamic effect is measured by 'seroconversion'—the development of detectable antibodies.

• Onset: Antibodies are typically detectable 15 days after the first dose.
• Peak Effect: Maximum antibody titers are reached approximately 1 month after the first dose.
• Duration: While the first dose provides protection for at least one year, the second (booster) dose induces a 'memory' response that is estimated to provide protection for 20 to 40 years, and likely for life in most individuals.

| Parameter | Value |

|---|---|

| Bioavailability | N/A (Intramuscular Injection) |

| Protein Binding | N/A |

| Half-life (Antibodies) | ~21 days (IgG) |

| Tmax (Antibody Response) | 15–30 days post-injection |

| Metabolism | Cellular proteolysis |

| Excretion | Cellular clearance |

The antigen consists of the whole Hepatitis A virus (HM175 strain) that has been inactivated. The molecular structure is that of a non-enveloped, positive-sense RNA virus (Picornaviridae family). The inactivation process uses formaldehyde (HCHO), which cross-links viral proteins, rendering the virus unable to replicate while preserving the antigenicity of the VP1, VP2, and VP3 proteins on the viral capsid. The vaccine is typically adsorbed onto aluminum hydroxide (Al(OH)3), which acts as an adjuvant to enhance the immune response.

This agent is classified as an Inactivated Viral Vaccine. It is distinct from live-attenuated vaccines (like MMR) because it contains no living material. Within the Established Pharmacologic Class (EPC), it is specifically an Inactivated Hepatitis A Virus Vaccine [EPC]. It may also be found in combination products classified as Inactivated Hepatitis B Virus Vaccine [EPC] when paired with HBsAg.