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Influenza Virus Vaccine (Recombinant)


(in floo EN za VYE rus vak SEEN ree KOM be nant)

Index Terms

  • Recombinant Influenza Vaccine, Trivalent
  • RIV
  • RIV3
  • Trivalent Recombinant Hemagglutinin (rHA) Vaccine

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Solution, Intramuscular [preservative free]:

Flublok: (0.5 mL) [no egg protein]

Brand Names: U.S.

  • Flublok

Pharmacologic Category

  • Vaccine
  • Vaccine, Recombinant


Promotes immunity to seasonal influenza virus by inducing specific antibody production. Each year the formulation is standardized according to the US Public Health Service. Preparations from previous seasons must not be used.

Onset of Action

Most adults have antibody protection within 2 weeks of vaccination (CDC/ACIP [Grohskopf 2013]).

Duration of Action

When vaccine is antigenically similar to circulating virus ≥6 to 8 months (CDC/ACIP [Grohskopf 2013]); response may be diminished in persons ≥65 years and limited evidence suggests titers may decline significantly 6 months following vaccination in this population (ACIP [Grohskopf 2015]).

Use: Labeled Indications

Influenza disease prevention: Active immunization against influenza disease caused by influenza virus subtypes A and type B contained in the vaccine in persons 18 years of age and older

The Advisory Committee on Immunization Practices (ACIP) recommends routine annual vaccination with seasonal influenza vaccine for all persons ≥6 months who do not otherwise have contraindications to the vaccine. ACIP recommends use of any age and risk factor appropriate product. Persons 18 years of age and older may receive vaccination with the recombinant influenza vaccine (RIV). In addition to RIV, other products are available for certain patient populations: Healthy nonpregnant persons aged 2 to 49 years may receive vaccination with the live attenuated influenza vaccine (LAIV). Persons ≥6 months of age may receive the trivalent inactivated influenza vaccine (IIV3) or the quadrivalent inactivated influenza vaccine (IIV4) (ACIP [Grohskopf 2015]).

When vaccine supply is limited, target groups for vaccination (those at higher risk of complications from influenza infection and their close contacts) include the following (CDC/ACIP [Grohskopf 2013]):

• infants and children 6 to 59 months of age

• Persons ≥50 years of age

• Residents of nursing homes and other long-term care facilities

• Patients with chronic pulmonary disorders (including asthma) or cardiovascular systems disorders (except hypertension), renal, hepatic, neurologic, or metabolic disorders (including diabetes mellitus)

• Persons who have immunosuppression (including immunosuppression caused by medications or HIV)

• Infants, children, and adolescents (6 months to 18 years of age) who are receiving long-term aspirin therapy, and therefore, may be at risk for developing Reye syndrome after influenza

• Women who are or will be pregnant during the influenza season

• Healthcare personnel

• Household contacts (including children) and caregivers of neonates, infants, and children <5 years (particularly children <6 months) and adults ≥50 years

• Household contacts (including children) and caregivers of persons with medical conditions which put them at high risk of complications from influenza infection

• American Indians/Alaska Natives

• Morbidly obese (BMI ≥40)


Severe allergic reaction (eg, anaphylaxis) to any component of the vaccine

Dosing: Adult

It is important to note that influenza seasons vary in their timing and duration from year to year. In general, vaccination should begin soon after the vaccine becomes available (and, if possible, by October) and prior to onset of influenza activity in the community. However, vaccination should continue throughout the influenza season as long as vaccine is available (ACIP [Grohskopf 2015]).

Immunization: Flublok: IM: Adults: 0.5 mL/dose (1 per season)

Dosing: Geriatric

Refer to adult dosing.

Dosing: Renal Impairment

There are no dosage adjustments provided in the manufacturer’s labeling.

Dosing: Hepatic Impairment

There are no dosage adjustments provided in the manufacturer’s labeling.


For IM administration only. Shake gently prior to use. Inspect for particulate matter and discoloration prior to administration. Avoiding use if visible particles are present in the solution after shaking. Adults should be vaccinated in the deltoid muscle. Do not inject into the gluteal region or areas where there may be a major nerve trunk. To prevent syncope related injuries, adolescents and adults should be vaccinated while seated or lying down (NCIRD/ACIP 2011). US law requires that the date of administration, the vaccine manufacturer, lot number of vaccine, and the administering person's name, title, and address be entered into the patient's permanent medical record.

Unless otherwise indicated in product labeling, jet injectors should not be used to administer inactivated influenza vaccines (CDC/ACIP [Grohskopf 2013]). Currently, Afluria is the only influenza vaccine licensed in the United States that can be given by a jet-injector device).

Note: For patients at risk of hemorrhage following intramuscular injection, the vaccine should be administered intramuscularly if, in the opinion of the physician familiar with the patient's bleeding risk, the vaccine can be administered by this route with reasonable safety. If the patient receives antihemophilia or other similar therapy, intramuscular vaccination can be scheduled shortly after such therapy is administered. A fine needle (23 gauge or smaller) can be used for the vaccination and firm pressure applied to the site (without rubbing) for at least 2 minutes. The patient should be instructed concerning the risk of hematoma from the injection. Patients on anticoagulant therapy should be considered to have the same bleeding risks and treated as those with clotting factor disorders (NCIRD/ACIP 2011).


Do not mix with other vaccines or injections. Separate needles and syringes should be used for each injection.


Store between 2°C to 8°C (36°F to 46°F). Protect from light. Do not freeze. Discard if frozen.

Adverse Reactions

All serious adverse reactions must be reported to the U.S. Department of Health and Human Services (DHHS) Vaccine Adverse Event Reporting System (VAERS) 1-800-822-7967 or online at In Canada, adverse reactions may be reported to local provincial/territorial health agencies or to the Vaccine Safety Section at Public Health Agency of Canada (1-866-844-0018).


Central nervous system: Headache (older adults 10% to 17%), fatigue (13% to 15%)

Local: Pain at injection site (37%, older adults 19% to 32%)

Neuromuscular & skeletal: Myalgia (8% to 11%)

1% to 10%:

Central nervous system: Chills (older adults 5%)

Gastrointestinal: Nausea (4% to 6%)

Local: Injection site reactions (3% to 7%; includes redness, swelling and firmness)

Neuromuscular & skeletal: Arthralgia (older adults 6% to 8%)

Respiratory: Cough (1% to 2%), nasal congestion (1% to 2%), nasopharyngitis (1% to 2%), pharyngolaryngeal pain (1% to 2%), rhinorrhea (1% to 2%), upper respiratory tract infection (1% to 2%)

<1% (Limited to important or life-threatening): Hypersensitivity reaction, pleuropericarditis


Concerns related to adverse effects:

• Anaphylactoid/hypersensitivity reactions: Immediate treatment (including epinephrine 1 mg/mL) for anaphylactoid and/or hypersensitivity reactions should be available during vaccine use (NCIRD/ACIP 2011).

• Syncope: Syncope has been reported with use of injectable vaccines and may result in serious secondary injury (eg, skull fracture, cerebral hemorrhage); typically reported in adolescents and young adults and within 15 minutes after vaccination. Procedures should be in place to avoid injuries from falling and to restore cerebral perfusion if syncope occurs (NCIRD/ACIP 2011).

Disease-related concerns:

• Acute illness: The decision to administer or delay vaccination because of current or recent febrile illness depends on the severity of symptoms and the etiology of the disease. Consider deferring administration in patients with moderate or severe acute illness (with or without fever); vaccination should not be delayed for patients with mild acute illness (with or without fever) (NCIRD/ACIP 2011).

• Bleeding disorders: Use with caution in patients with a history of bleeding disorders (including thrombocytopenia) and/or patients on anticoagulant therapy; bleeding/hematoma may occur from IM administration; if the patient receives antihemophilia or other similar therapy, IM injection can be scheduled shortly after such therapy is administered (NCIRD/ACIP 2011).

• Guillain-Barré syndrome: Use with caution in patients with history of Guillain-Barré syndrome (GBS); patients with history of GBS have a greater likelihood of developing GBS than those without. As a precaution, the ACIP recommends that patients with a history of GBS and who are at low risk for severe influenza complications, and patients known to have experienced GBS within 6 weeks following previous vaccination should generally not be vaccinated (consider influenza antiviral chemoprophylaxis in these patients). The benefits of vaccination may outweigh the potential risks in persons with a history of GBS who are also at high risk for complications of influenza. Influenza infection itself may cause Guillain-Barré syndrome (CDC/ACIP [Grohskopf 2013]). Recent studies of patients who received the trivalent inactivated influenza vaccine or the monovalent H1N1 influenza vaccine have shown the risk of GBS is lower with vaccination than with influenza infection (Baxter 2013; Greene 2013; Kwong 2013).

Concurrent drug therapy issues:

• Vaccines: In order to maximize vaccination rates, the ACIP recommends simultaneous administration (ie, >1 vaccine on the same day at different anatomic sites) of all age-appropriate vaccines (live or inactivated) for which a person is eligible at a single clinic visit, unless contraindications exist. The ACIP prefers each dose of a specific vaccine in a series come from the same manufacturer when possible (NCIRD/ACIP 2011).

Special populations:

• Altered immunocompetence: Use with caution in severely-immunocompromised patients (eg, patients receiving chemo/radiation therapy or other immunosuppressive therapy [including high-dose corticosteroid]); may have a reduced response to vaccination. Inactivated vaccine (IIV or RIV) is preferred over live virus vaccine for household members, healthcare workers and others coming in close contact with severely-immunosuppressed persons requiring care in a protected environment (ACIP [Grohskopf 2015]; NCIRD/ACIP 2011); inactivated vaccines should be administered ≥2 weeks prior to planned immunosuppression when feasible (IDSA [Rubin 2014]).

• Pediatric: In a clinical trial of infants and children 6 months through 3 years of age, a decreased response to Flublok was reported compared to currently licensed US influenza vaccine for this population, suggesting that it would not be effective in children ≤3 years; safety and efficacy in older pediatric patients have not been established; use has not been studied.

Dosage form specific issues:

• Flublok is a trivalent influenza vaccine produced using continuous insect cell lines. It is a recombinant hemagglutinin (rHA) vaccine; it does not use the influenza virus or eggs in its production process. ACIP states it may be used in persons with an egg allergy of any severity if otherwise appropriate (ACIP [Grohskopf 2015]).

Other warnings/precautions:

• Appropriate use: Use of this vaccine for specific medical and/or other indications (eg, immunocompromising conditions, hepatic or kidney disease, diabetes) is also addressed in the ACIP Recommended Adult Immunization Schedule (ACIP [Kim 2016]).

• Effective immunity: Vaccination may not result in effective immunity in all patients. Response depends upon multiple factors (eg, type of vaccine, age of patient) and may be improved by administering the vaccine at the recommended dose, route, and interval. Vaccines may not be effective if administered during periods of altered immune competence (NCIRD/ACIP 2011).

• Previous season vaccines: Influenza vaccines from previous seasons must not be used (CDC/ACIP [Grohskopf 2013]).

Monitoring Parameters

Monitor for syncope for 15 minutes following administration (NCIRD/ACIP 2011). If seizure-like activity associated with syncope occurs, maintain patient in supine or Trendelenburg position to reestablish adequate cerebral perfusion.

Pregnancy Risk Factor


Pregnancy Considerations

Adverse events were not observed in animal reproduction studies. Information specific to the use of RIV in pregnancy has not been located.

Pregnant women are at an increased risk of complications from influenza infection (Rasmussen 2008). Influenza vaccination with the inactivated influenza vaccine (IIV) is recommended for all women who are or will become pregnant during the influenza season and who do not otherwise have contraindications to the vaccine (CDC/ACIP 62[07] 2013).

Pregnant women should observe the same precautions as nonpregnant women to reduce the risk of exposure to influenza and other respiratory infections (CDC/HHS 2010). When vaccine supply is limited, focus on delivering the vaccine should be given to women who are pregnant or will be pregnant during the flu season, as well as mothers of newborns and contacts or caregivers of children <5 years of age (CDC/ACIP 62[07] 2013).

Health care providers are encouraged to refer women exposed to the influenza vaccine during pregnancy to the Vaccines and Medications in Pregnancy Surveillance System (VAMPSS) by contacting The Organization of Teratology Information Specialists (OTIS) at (877) 311-8972. Women exposed to this vaccine during pregnancy may also contact the Flublok pregnancy registry at 888-855-7871.

Patient Education

• Discuss specific use of vaccine and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience injection site pain, headache, muscle pain, loss of strength and energy, or nausea (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.