Influenza B Virus B/washington/02/2019 Antigen (formaldehyde Inactivated)

For adults aged 18 to 64 years, the standard dose of the vaccine containing the B/Washington/02/2019 antigen is a single 0.5 mL intramuscular injection. This dose typically contains 15 micrograms (mcg) of the hemagglutinin (HA) protein from this specific B strain, along with 15 mcg from each of the other three strains (A/H1N1, A/H3N2, and another B strain). For adults aged 65 years and older, a high-dose formulation may be administered, which contains 60 mcg of the B/Washington/02/2019 HA antigen per 0.7 mL dose to overcome immunosenescence (the natural weakening of the immune system with age).

Pediatric dosing is strictly age-dependent according to CDC and FDA guidelines:

• Children 6 months through 35 months: The dose may be 0.25 mL or 0.5 mL depending on the specific brand of vaccine (e.g., Fluzone vs. Fluarix).
• Children 3 years through 8 years: A single 0.5 mL dose is standard. However, if the child has not received at least two prior doses of influenza vaccine before July 1st of the current year, they require two doses administered at least 4 weeks apart to ensure adequate priming of the immune system.
• Children 9 years and older: A single 0.5 mL dose is sufficient, regardless of prior vaccination history.

Renal Impairment

No dosage adjustment is required for patients with renal impairment. The antigen is not cleared by the kidneys in a manner that would lead to systemic toxicity.

Hepatic Impairment

No dosage adjustment is required for patients with hepatic impairment. The liver is not involved in the processing or clearance of the viral antigen.

Elderly Patients

While the standard 0.5 mL dose is safe, patients over 65 are often encouraged to receive the High-Dose or Adjuvanted formulations to ensure a more robust protective antibody titer.

This medication is administered exclusively by a healthcare professional. It is given as an intramuscular (IM) injection. In adults and older children, the preferred site is the deltoid muscle of the upper arm. In infants and small children, the anterolateral aspect of the thigh is the preferred site.

Before administration, the vaccine should be inspected for particulate matter or discoloration. It should be shaken well to maintain the suspension. The vaccine must be stored in a refrigerator between 2°C and 8°C (36°F to 46°F) and must never be frozen. If the vaccine has been frozen, it must be discarded. It is typically administered without regard to food intake.

Influenza vaccines are seasonal. If you miss your annual flu shot, you should receive it as soon as possible, provided the influenza virus is still circulating in your community (typically through late spring). For children requiring two doses, if the second dose is missed, it should be administered as soon as it is remembered, even if more than 4 weeks have passed.

An overdose of this antigen is highly unlikely as it is administered in pre-filled syringes or measured vials by clinicians. In the event of an accidental double-dose, the primary risk is an increase in the severity of local injection site reactions (swelling, pain) or systemic symptoms (fever). There is no specific "antidote"; treatment is supportive, focusing on fever reduction and hydration. In case of suspected overdose, contact your local poison control center or seek emergency medical care.

> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose without medical guidance. Ensure your immunization record is updated after each administration.

The most frequently reported side effects associated with the Influenza B/Washington/02/2019 antigen are local reactions at the site of injection. These occur because the immune system is actively responding to the foreign viral proteins.

• Injection Site Pain: Up to 65% of recipients experience mild to moderate soreness in the deltoid or thigh. This typically begins within 6 hours and resolves within 48 hours.
• Erythema (Redness): Redness at the site is common and usually measures less than 2 cm.
• Induration (Hardness) and Swelling: A small, firm area may develop at the needle entry point.
• Fatigue and Malaise: A general feeling of tiredness or being 'under the weather' is reported by approximately 15-20% of patients.
• Headache: Mild tension-type headaches are common in adults.

• Myalgia (Muscle Aches): Generalized muscle soreness, similar to the early stages of a viral illness, may occur.
• Arthralgia (Joint Pain): Stiffness or pain in the joints, particularly in the limb where the injection was given.
• Low-grade Fever: A temperature between 99.5°F and 101°F, especially in children.
• Nausea and Chills: These systemic symptoms are usually transient and do not require medical intervention.
• Lymphadenopathy: Swelling of the lymph nodes in the axilla (armpit) on the side of the injection.

• Syncope (Fainting): Most common in adolescents, often related to the anxiety of the injection rather than the antigen itself.
• Urticaria (Hives): A localized or generalized itchy rash.
• Severe Local Reactions: Swelling that extends from the shoulder to the elbow.

While extremely rare, serious adverse events can occur.

> Warning: Stop taking Influenza B Virus B/washington/02/2019 Antigen (formaldehyde Inactivated) and call your doctor immediately if you experience any of these.

• Anaphylaxis: A severe allergic reaction characterized by difficulty breathing, swelling of the face or throat, rapid heartbeat, and a sharp drop in blood pressure. This typically occurs within minutes of injection.
• Guillain-Barré Syndrome (GBS): A neurological disorder where the body's immune system attacks the nerves. Symptoms include weakness or tingling in the legs that spreads to the upper body, which can lead to paralysis. The estimated risk is 1 to 2 additional cases per million doses.
• Shoulder Injury Related to Vaccine Administration (SIRVA): Severe, persistent pain and limited range of motion in the shoulder caused by the needle being injected too high or too deep into the joint space.
• Facial Palsy (Bell's Palsy): Sudden weakness in the facial muscles, though a causal link to the B/Washington antigen is not firmly established.

There are no known long-term side effects associated with the B/Washington/02/2019 antigen. The antigen is cleared from the body within days, and the immune response (antibodies) is a natural physiological process. Unlike some medications, there is no risk of organ accumulation or chronic toxicity.

No FDA black box warnings exist for Influenza B Virus B/washington/02/2019 Antigen (formaldehyde Inactivated). It is generally considered safe for the vast majority of the population, including those with stable chronic health conditions.

Report any unusual symptoms to your healthcare provider. You are also encouraged to report negative side effects to the Vaccine Adverse Event Reporting System (VAERS) at 1-800-822-7967.

Influenza B Virus B/washington/02/2019 Antigen is intended for intramuscular use only. It must not be administered intravenously, as this could trigger a systemic inflammatory response. Patients should be screened for any history of severe allergic reactions to previous influenza vaccinations or any components of the vaccine, including egg proteins, formaldehyde (used in the inactivation process), or surfactants like Triton X-100.

No FDA black box warnings for Influenza B Virus B/washington/02/2019 Antigen (formaldehyde Inactivated).

• Allergic Reactions / Anaphylaxis Risk: Epinephrine (1:1000) and other appropriate agents used to control immediate allergic reactions must be immediately available should an acute anaphylactic reaction occur following administration.
• Guillain-Barré Syndrome (GBS): If GBS has occurred within 6 weeks of previous influenza vaccination, the decision to give the B/Washington/02/2019 antigen should be based on careful consideration of the potential benefits and risks.
• Altered Immunocompetence: In patients who are immunocompromised (due to HIV, cancer, or immunosuppressive therapy), the immune response to the antigen may be diminished. This does not mean the vaccine is unsafe, but it may be less effective at preventing the flu.
• Acute Febrile Illness: Vaccination should typically be delayed in patients with moderate or severe acute illness, with or without fever, until the condition has resolved. This prevents the confusion of symptoms between the underlying illness and potential vaccine side effects.

Patients should be observed for at least 15 minutes after receiving the injection to monitor for immediate allergic reactions or syncope (fainting). No routine laboratory monitoring (e.g., blood counts or liver function tests) is required after administration. In clinical trials, immunogenicity is monitored via Hemagglutination Inhibition (HI) antibody titers, but this is not performed in standard clinical practice.

The antigen has no known effect on the ability to drive or operate machinery. However, if a patient experiences post-vaccination syncope or significant fatigue, they should avoid these activities until symptoms resolve.

There is no direct interaction between alcohol and the Influenza B/Washington antigen. However, heavy alcohol consumption can suppress the immune system, potentially reducing the effectiveness of the body's response to the vaccine. Moderate consumption is generally not considered a contraindication.

As this is a single-dose seasonal intervention, "discontinuation" in the traditional sense does not apply. However, if a patient experiences a severe reaction to the B/Washington/02/2019 strain, they should not receive subsequent doses of vaccines containing this specific antigen or related Victoria-lineage B strains in future seasons without specialist consultation.

> Important: Discuss all your medical conditions with your healthcare provider before starting Influenza B Virus B/washington/02/2019 Antigen (formaldehyde Inactivated). Inform them if you have a history of bleeding disorders, as IM injections can cause hematomas.

There are no absolute drug-drug contraindications that would result in a life-threatening interaction; however, certain combinations are avoided to ensure vaccine efficacy.

• Live Attenuated Vaccines: While inactivated antigens like B/Washington/02/2019 can usually be given with other inactivated vaccines, they should not be mixed in the same syringe. If a live vaccine (like the nasal spray flu vaccine) is being considered, it is generally not given alongside the inactivated injection.

• Immunosuppressive Therapies: Drugs such as high-dose corticosteroids (e.g., Prednisone >20mg/day), chemotherapy, and biologics (e.g., Rituximab, Infliximab) can significantly blunt the immune system's response to the B/Washington antigen. The clinical consequence is reduced vaccine efficacy. Management may involve timing the vaccination during a "window" when immunosuppression is at its lowest.
• Anticoagulants and Antiplatelets: Medications like Warfarin (Coumadin), Apixaban (Eliquis), or Clopidogrel (Plavix) increase the risk of bleeding and hematoma at the injection site. The injection should be administered with a fine needle, and firm pressure should be applied for at least two minutes afterward.

• Antiviral Medications: While neuraminidase inhibitors (like Oseltamivir/Tamiflu) do not interfere with inactivated vaccines, they may interfere with live vaccines. For the inactivated B/Washington antigen, there is no significant interaction.
• Statins: Some studies suggest that chronic statin use might slightly reduce the antibody response to influenza antigens in the elderly, though the clinical impact is considered minor and does not warrant stopping the medication.

There are no known interactions between the B/Washington/02/2019 antigen and specific foods. The presence of egg protein in the manufacturing process is a concern for those with severe egg allergies, though most modern guidelines suggest that even those with egg allergies can safely receive the vaccine in a medical setting.

• Echinacea and Elderberry: These are often taken to "boost" the immune system. While there is no evidence of harm, there is also no clinical data suggesting they improve the seroconversion rate of the B/Washington antigen.
• High-dose Vitamin C: No known interaction.

• False Positive HIV/HCV/HTLV-1 Tests: Following influenza vaccination, transient false-positive results in certain enzyme immunoassays (EIA) for HIV-1, Hepatitis C, and HTLV-1 have been reported. This is due to the cross-reactive IgM response. If a positive result occurs shortly after vaccination, confirmatory testing (e.g., Western Blot or PCR) should be performed.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, especially if you are undergoing treatment that affects your immune system.

Influenza B Virus B/washington/02/2019 Antigen (formaldehyde Inactivated) must NEVER be used in the following circumstances:

• Severe Allergic Reaction (Anaphylaxis): Any individual with a documented history of anaphylaxis to a previous dose of an influenza vaccine or to any specific component of the vaccine (e.g., formaldehyde, egg protein, neomycin used in production) must not receive the antigen. The mechanism is an IgE-mediated hypersensitivity that can lead to airway obstruction and circulatory collapse.
• Infants under 6 months of age: The safety and efficacy of the B/Washington antigen have not been established in this age group. Furthermore, the infant's immune system may not respond appropriately, and maternal antibodies may interfere with the response.

Conditions requiring careful risk-benefit analysis include:

• History of Guillain-Barré Syndrome (GBS): If GBS occurred within 6 weeks of a prior flu shot, the risk of recurrence is theoretically present, although data is inconclusive. Healthcare providers will weigh the risk of severe flu complications against the rare risk of GBS recurrence.
• Moderate to Severe Acute Illness: Vaccination should be deferred until the patient has recovered to ensure that side effects of the vaccine do not mask the progression of the illness.
• Bleeding Disorders: In patients with hemophilia or severe thrombocytopenia, the risk of intramuscular hematoma is high. A subcutaneous route is sometimes used off-label, though this may reduce immunogenicity.

Patients who are sensitive to formaldehyde may react to the trace amounts remaining in the vaccine after the inactivation process. Similarly, those with sensitivities to polysorbate 80 or neomycin (if used by the specific manufacturer) should check the package insert of the specific vaccine brand containing the B/Washington/02/2019 antigen.

> Important: Your healthcare provider will evaluate your complete medical history before prescribing Influenza B Virus B/washington/02/2019 Antigen (formaldehyde Inactivated).

Influenza B Virus B/washington/02/2019 Antigen is considered safe and is highly recommended for pregnant individuals. The CDC and ACOG (American College of Obstetricians and Gynecologists) recommend vaccination during any trimester. Pregnant women are at increased risk for severe complications from Influenza B, including pneumonia and premature labor. Studies have shown that the inactivated antigen does not cause teratogenicity (birth defects). Furthermore, vaccination during pregnancy provides "passive immunity" to the newborn, protecting the infant during the first six months of life when they are too young to be vaccinated themselves.

There is no evidence that the inactivated B/Washington antigen or the resulting antibodies interfere with breastfeeding. The antigen does not pass into breast milk in a form that would affect the infant. Breastfeeding mothers can safely receive the vaccine to protect themselves and reduce the risk of transmitting the virus to their infants.

Approved for use in children 6 months and older. In children under 9 years old who are receiving the flu vaccine for the first time, a two-dose series is required. The B/Washington/02/2019 antigen has been shown to be immunogenic in pediatric populations, though febrile seizures are a very rare risk in young children when the flu vaccine is given simultaneously with certain other pediatric vaccines (like PCV13).

Adults 65 years and older are at the highest risk for mortality from Influenza B. While the standard B/Washington antigen is safe, this population often exhibits a lower antibody response. Therefore, the use of High-Dose (Fluzone High-Dose) or Adjuvanted (Fluad) vaccines is preferred. These formulations contain the same B/Washington/02/2019 antigen but in higher quantities or with an added substance to boost the immune response.

No dosage adjustments are needed. Patients on hemodialysis can safely receive the antigen, although their immune response may be slightly blunted compared to the general population. It is often recommended to vaccinate these patients at least 2 weeks before starting intensive immunosuppressive cycles if possible.

No adjustments are required for patients with cirrhosis or other liver diseases. The antigen processing occurs in the lymphatic and immune systems, bypassing hepatic metabolic pathways.

> Important: Special populations require individualized medical assessment to determine the most appropriate vaccine formulation.

The Influenza B Virus B/washington/02/2019 Antigen acts as a primary immunogen. The specific molecular target is the Hemagglutinin (HA) protein. In the native virus, HA binds to sialic acid on host cells to initiate infection. The inactivated antigen presents an identical HA structure to the immune system. B-lymphocytes recognize the epitopes (binding sites) on the HA protein, leading to the production of neutralizing antibodies. These antibodies provide a "lock and key" fit that prevents future live viruses from docking with human cells. This antigen also contains Neuraminidase (NA), which helps the immune system generate antibodies that can limit the release of viral particles from infected cells, further reducing viral spread within the host.

The pharmacodynamic effect is measured by the rise in serum antibody titers. The most common metric is the Hemagglutination Inhibition (HI) titer. A titer of 1:40 or greater is generally accepted as the threshold for a 50% reduction in the risk of contracting influenza. The onset of this effect is not immediate; it requires 14 to 21 days for the immune system to generate a sufficient concentration of IgG antibodies. The duration of effect typically lasts 6 to 12 months, which is why annual revaccination is required as antibody levels naturally wane.

| Parameter | Value |

|---|---|

| Bioavailability | N/A (Intramuscular Injection) |

| Protein Binding | N/A (Processed by APCs) |

| Half-life (Antigen) | ~12-48 hours |

| Tmax (Antibody Response) | 2-4 weeks |

| Metabolism | Proteolytic degradation in lysosomes |

| Excretion | Renal (as amino acid metabolites) |

The antigen consists of inactivated viral fragments. The B/Washington/02/2019 strain is a Victoria-lineage virus. The chemical process involves the use of Formaldehyde to cross-link viral surface proteins, rendering the RNA non-functional and the virus unable to replicate. The final product is a sterile, clear to slightly opalescent suspension. It is standardized to contain exactly 15 mcg (standard dose) or 60 mcg (high dose) of HA per strain.

It is classified as a Vaccine, Inactivated, Viral. Within the FDA's Established Pharmacologic Class (EPC), it is categorized as a Standardized Chemical Allergen [EPC]. It is often grouped with other seasonal antigens in quadrivalent (four-strain) formulations.