Inactivated Influenza Vaccine

• Prevention of Influenza Virus Infection:
  Active immunization to prevent seasonal influenza caused by influenza A and B viruses.
• Seasonal Vaccination:
  Recommended annually for individuals aged 6 months and older before the start of the influenza season.
• High-Risk Groups:
• Adults aged 65 years and older
• Children aged 6 months to 59 months
• Pregnant women at any stage of pregnancy
• Persons with chronic medical conditions (such as asthma, diabetes, cardiovascular disease, chronic lung or kidney disease, immunosuppression)
• Healthcare workers and caregivers of high-risk individuals
• Outbreak Control:
  Used to control influenza outbreaks in institutional settings such as nursing homes and hospitals.
• Off-Label Uses:
  No clinically accepted off-label indications.

• Adults and Children ≥36 Months:
• Single dose of 0.5 mL administered intramuscularly once yearly.
• Children 6 Months to 35 Months:
• Two doses of 0.25 mL each, administered at least four weeks apart during the first influenza season.
• In subsequent seasons, a single annual dose is recommended.
• Elderly (≥65 Years):
• Standard dosing is the same as for adults; however, high-dose or adjuvanted formulations may be preferred if available.
• Special Populations:
• No dose adjustments required for individuals with renal or hepatic impairment.
• Immunocompromised patients should receive the vaccine but may have a reduced immune response.
• Route of Administration:
  Intramuscular injection, preferably in the deltoid muscle for adults and anterolateral thigh for young children.
• Timing:
  Administer prior to the influenza season, ideally 2 weeks before expected exposure, as immunity develops within 10 to 14 days.

The inactivated influenza vaccine contains purified, chemically inactivated influenza virus antigens, primarily hemagglutinin (HA) and neuraminidase (NA) proteins from circulating influenza A and B strains. Upon intramuscular administration, these antigens stimulate the immune system to produce strain-specific antibodies. These antibodies neutralize the influenza virus by blocking viral attachment and entry into respiratory epithelial cells, thus preventing infection or reducing disease severity upon exposure.

• Absorption: The vaccine antigens are absorbed locally at the injection site, where antigen-presenting cells initiate the immune response.
• Distribution: Antigens are presented in local lymph nodes to B and T lymphocytes, activating adaptive immunity.
• Metabolism: The vaccine antigens are processed by immune cells; no systemic metabolism occurs.
• Excretion: Not applicable, as vaccine components are non-replicating and non-systemic.
• Onset of Immunity: Protective antibody titers develop within 10 to 14 days post-vaccination.
• Duration of Immunity: Immunity lasts approximately 6 months, necessitating annual vaccination due to antigenic drift.

• Pregnancy:
  Classified as FDA Pregnancy Category B. The vaccine is safe and recommended for use at any stage of pregnancy to protect both mother and fetus from influenza complications.
• Lactation:
  Considered safe during breastfeeding with no known adverse effects on the infant.

• Primary Class: Viral Vaccine
• Subclass: Inactivated Influenza Virus Vaccine

• Known severe hypersensitivity to any vaccine component, including egg proteins (except when egg-free formulations are used).
• History of severe allergic reaction (anaphylaxis) after prior influenza vaccination.
• Moderate or severe acute illness with or without fever; vaccination should be deferred until recovery.

• Individuals with a history of Guillain-Barré syndrome within 6 weeks of prior influenza vaccination should consult healthcare providers before vaccination.
• Patients with egg allergy can receive the vaccine under medical supervision or use egg-free vaccine formulations.
• Immunocompromised individuals may have a reduced immune response.
• Observe for at least 15 minutes post-vaccination to monitor for immediate allergic reactions.
• No black box warnings are associated with this vaccine.

• Common:
• Local injection site reactions: pain, redness, swelling.
• Systemic: mild fever, fatigue, headache, myalgia.
• Uncommon:
• Allergic skin reactions such as rash or urticaria.
• Rare:
• Anaphylaxis (extremely rare).
• Guillain-Barré syndrome (very rare; causal relationship unclear).
• Side effects generally appear within hours to a few days after vaccination and resolve spontaneously.

• No clinically significant interactions with medications have been reported.
• Immunosuppressive therapy may reduce vaccine efficacy.
• Safe to administer concomitantly with other vaccines at different injection sites.
• No known interactions with food or alcohol.

• Annual reformulation of vaccine strains is based on global influenza surveillance coordinated by WHO.
• Current guidelines recommend annual vaccination of all persons aged 6 months and older.
• Egg-free and adjuvanted vaccine formulations have been introduced to improve safety and efficacy in special populations.
• Continued recommendation for vaccination during pregnancy and for healthcare personnel.
• Ongoing post-marketing surveillance confirms vaccine safety.

• Store refrigerated at 2°C to 8°C (36°F to 46°F).
• Protect from freezing, as freezing damages the vaccine.
• Protect from light exposure.
• Shake well before administration.
• Use promptly after opening; discard according to manufacturer instructions.