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Generic Name: Influenza Vaccine Recombinant
Class: Vaccines
VA Class: IM100


Recombinant influenza vaccine.1 Seasonal influenza vaccine recombinant contains recombinant hemagglutinin (HA) proteins representing influenza virus types A and B likely to circulate in the US during the upcoming season and is used to stimulate active immunity to influenza strains contained in the vaccine.1 100 567

Uses for Flublok

Prevention of Seasonal Influenza A and B Virus Infections

Prevention of seasonal influenza virus infection in adults ≥18 years of age.1 100

Influenza is an acute viral infection; influenza viruses spread from person to person mainly through large-particle respiratory droplet transmission.100 166 In the US, annual epidemics of seasonal influenza occur, usually during the fall or winter.100 Influenza viruses can cause illness in any age group; children have highest rate of infection.100 166 Influenza can exacerbate underlying medical conditions or lead to pneumonia in certain individuals.100 166 Adults ≥65 years of age, children <2 years of age, and individuals with chronic medical conditions have highest risk of influenza-related complications and death.100 166

Annual vaccination is the primary means of preventing seasonal influenza and its complications.100

US Public Health Service Advisory Committee on Immunization Practices (ACIP), AAP, and others recommend routine influenza vaccination for all adults, adolescents, and infants and children ≥6 months of age using an age-appropriate seasonal influenza vaccine, unless contraindicated.100 112 199 200 235 Vaccination against seasonal influenza recommended for otherwise healthy individuals as well as those who have medical conditions that put them at increased risk for influenza-related complications or at higher risk for influenza-related outpatient, emergency department, or hospital visits.100 112

Select specific seasonal influenza vaccine based on individual's age and whether they have certain underlying medical conditions that put them at increased risk of influenza complications (e.g., pregnancy, immunocompromising disease or therapy), are in close contact with severely immunocompromised individuals, or have a personal history that contraindicates use of certain vaccines.100 112 For many individuals, more than one vaccine type may be appropriate.100 112

ACIP and AAP state there are no preferential recommendations for any specific vaccine type or trade name, provided an age-appropriate vaccine is chosen based on FDA-labeled indications and contraindications.100 112 In addition, these experts do not state a preference for a trivalent or quadrivalent formulation for the 2016–2017 influenza season.100 112 If an age-appropriate vaccine is available and there are no contraindications, do not delay influenza vaccination to obtain a specific product.100 112

Travelers (including those at high risk for influenza complications) who were not vaccinated during the preceding fall or winter should receive seasonal influenza vaccine ≥2 weeks before departure if they will be traveling to the tropics, traveling to the Southern Hemisphere from April through September, or traveling with organized tourist groups at any time of the year.115 Revaccination not recommended for travelers who received influenza vaccine during the preceding fall and will be traveling during the summer.115 Risk for exposure to seasonal influenza during travel depends on time of year and destination.115 In the Northern Hemisphere, influenza season may begin as early as October and extend until May;115 in the Southern Hemisphere, influenza season may begin in April and last through September.115 In tropical and subtropical areas, influenza viruses usually circulate throughout the year, but influenza activity may peak during rainy or dry seasons.115

Seasonal influenza vaccines not effective against all possible strains of influenza, but may be effective against those strains (and possibly closely related strains) represented in the vaccines.100 166

Current information regarding influenza surveillance and updated recommendations for prevention and treatment of seasonal influenza is available from CDC at .

Flublok Dosage and Administration


IM Injection

Administer by IM injection, preferably into deltoid.1 Do not administer IV, sub-Q, or intradermally.1

Shake vaccine vial gently before withdrawing dose.1 Vaccine should appear clear and colorless.1

To ensure delivery into muscle, make IM injections at a 90° angle to the skin using a needle length appropriate for individual's age and body mass.134

Do not mix with any other vaccine or solution.1

Administer seasonal influenza vaccine every year before exposure to seasonal influenza.100 112 In the US, localized outbreaks indicating start of the annual influenza season can occur as early as October;100 112 peak influenza activity (which often is close to the midpoint of influenza activity for the season) usually occurs in January through March;100 112 and influenza activity can continue until late spring (end of May).112

Offer influenza vaccination by the end of October, if possible, and continue to offer vaccination as long as influenza viruses are circulating and unexpired vaccine is available.100 112 To avoid missed opportunities for vaccination, offer influenza vaccination to unvaccinated individuals during routine health-care visits and hospitalizations when vaccine is available.100

Syncope (vasovagal or vasodepressor reaction; fainting) may occur following vaccination; such reactions occur most frequently in adolescents and young adults.134 Syncope and secondary injuries may be averted if vaccinees sit or lie down during and for 15 minutes after vaccination.134 If syncope occurs, observe patient until symptoms resolve.134



Prevention of Seasonal Influenza A and B Virus Infections
Adults ≥18 Years of Age

Single 0.5-mL dose.1

Special Populations

Hepatic Impairment

No specific dosage recommendations.1

Renal Impairment

No specific dosage recommendations.1

Geriatric Patients

Single 0.5-mL dose.1 (See Geriatric Use under Cautions.)

Cautions for Flublok


  • History of severe allergic reaction (e.g., anaphylaxis) to any component of the vaccine.1 (See Sensitivity Reactions under Cautions.)


Sensitivity Reactions

Anaphylaxis, anaphylactoid reactions, allergic reactions, and other forms of hypersensitivity reported during postmarketing experience.1 100

Prior to administration, review patient’s history with respect to possible sensitivity reactions to the vaccine or vaccine components and prior vaccination-related adverse effects and assess benefits versus risks.100 112

Appropriate medical treatment and supervision must be available for immediate use in case an anaphylactic reaction occurs.1

Guillain-Barré Syndrome (GBS)

If GBS occurred within 6 weeks after previous influenza vaccination, manufacturer states base decision to administer influenza vaccine on careful consideration of potential benefits and risks.1

Unclear whether influenza vaccination increases risk of recurrence of GBS.100 Temporal association was noted between administration of 1976 swine influenza vaccine and GBS.1 100 Investigations to date suggest no large increase in GBS associated with influenza vaccine (other than 1976 swine influenza vaccine) and if influenza vaccine does pose a risk it probably is quite small (i.e., approximately 1 additional case of GBS per 1 million vaccinees).1 100

ACIP states that, as a precaution, individuals who are not at high risk for severe influenza complications and who developed GBS within 6 weeks of a previous dose of influenza vaccine generally should not receive influenza vaccination;100 clinicians might consider use of antiviral prophylaxis for such individuals.100 However, ACIP states that benefits of influenza vaccine may outweigh risks for certain individuals with a history of GBS who are at high risk for severe complications from influenza.100

Individuals with Altered Immunocompetence

May be administered to individuals immunosuppressed as the result of disease or immunosuppressive therapy.1 Consider possibility that immune response to the vaccine and efficacy may be reduced in these individuals.1

Limitations of Vaccine Effectiveness

Following seasonal influenza vaccination, up to 2 weeks may be required to develop antibody protection against infection.100

May not protect all vaccine recipients from influenza.1

Seasonal influenza vaccines are formulated annually to contain influenza A and B antigens predicted to represent strains of influenza virus likely to circulate in the US during the upcoming influenza season.1 100 567 Efficacy of seasonal vaccine during any given year depends on how closely viral strains represented in the vaccine match viral strains circulating during the season.100 166

Concomitant Illness

Delay administration in individuals with moderate to severe acute illness (with or without fever) until symptoms have subsided.134

ACIP states that mild diarrhea or mild upper respiratory tract illness or other acute illness (with or without fever) does not preclude vaccination.134

Individuals with Bleeding Disorders

Advise individuals who have bleeding disorders or are receiving anticoagulant therapy and/or their family members about the risk of hematoma from IM injections.134

ACIP states that vaccines may be given IM to such individuals if a clinician familiar with the patient's bleeding risk determines that the injection can be administered with reasonable safety.134 In these cases, use a fine needle (23 gauge or smaller) to administer the vaccine and apply firm pressure to the injection site (without rubbing) for ≥2 minutes.134 If patient is receiving antihemophilia therapy, administer the IM vaccine shortly after a scheduled dose of such therapy.134

Improper Storage and Handling

Improper storage or handling of vaccines may reduce vaccine potency resulting in reduced or inadequate immune response in vaccinees.134

Inspect all vaccines upon delivery and monitor during storage to ensure that the appropriate temperature is maintained.134 (See Storage under Stability.)

Do not administer vaccine that has been mishandled or has not been stored at the recommended temperature.134 If there are concerns about mishandling, contact the manufacturer or state or local immunization or health departments for guidance on whether the vaccine is usable.134

Specific Populations


Category B.1

Manufacturer states use in pregnant women only when clearly needed.1

Pregnancy registry at 888-855-7871.1 Clinicians or vaccinees should report any exposure to the vaccine that occurs during pregnancy.1


Not known whether influenza vaccine recombinant is distributed into milk.1 Manufacturer recommends caution.1

Pediatric Use

Safety and efficacy not established in children or adolescents <18 years of age.1

Some evidence that influenza vaccine recombinant may not be effective in children <3 years of age.1

Geriatric Use

Some evidence that antibody responses are lower in adults ≥65 years of age compared with younger adults.1

Common Adverse Effects

Adults ≥18 years of age: Injection site reactions (e.g., pain), headache, fatigue, myalgia.1

Interactions for Flublok

Immunosuppressive Agents

Immune response may be decreased in individuals receiving immunosuppressive agents.1


Safety and immunogenicity of influenza vaccine recombinant administered concomitantly with age-appropriate inactivated or live vaccines not specifically studied.1




Injectable Solution, for IM Use

2–8°C; do not freeze.1 If freezing occurs, discard vaccine.1

Protect from light.1

Does not contain thimerosal or any other preservatives.1


  • Influenza vaccine recombinant contains recombinant hemagglutinin (HA) proteins from 3 suitable strains of influenza viruses.1 The vaccine is prepared using recombinant DNA technology and a continuous insect cell line (expresSF+) derived from Sf9 cells of the fall armyworm (Spodoptera frugiperda) and a baculovirus vector.1 Manufacturing process does not involve live influenza viruses and does not involve eggs.1

  • Seasonal influenza vaccines are formulated annually to contain antigens representative of the influenza A (H1N1), influenza A (H3N2), and influenza B viruses likely to circulate during the upcoming influenza season.1 100 567 For the 2016–2017 season, antigenic components recommended by FDA for US formulations of seasonal influenza vaccines are the same as those recommended by WHO (Northern Hemisphere).567 568

  • Influenza vaccine recombinant for the 2016–2017 influenza season is a trivalent vaccine containing 2 influenza type A antigens (H1N1 and H3N2) and a single influenza type B antigen (B/Victoria lineage).1 100 567 The 2016–2017 seasonal recombinant influenza vaccine for the US contains A/California/7/2009 (H1N1), A/Hong Kong/4801/2014 (H3N2), and B/Brisbane/60/2008 (B/Victoria lineage) HA antigens.1

  • Influenza vaccines stimulate active immunity to influenza virus strains represented in the vaccines.1

  • Following IM administration of influenza vaccine recombinant, the recombinant HA proteins contained in the vaccine act as antigens and induce a humoral immune response that can be measured by HA inhibition antibody.1

  • Following a single IM dose of trivalent influenza vaccine recombinant in adults 18 years of age and older during the 2007–2008 influenza season, an immune response to the H1N1, H3N2, and B components of the vaccine was achieved in 78, 81, and 52% of vaccine recipients, respectively;233 estimated vaccine effectiveness was 75% against influenza strains that closely matched vaccine strains and 45% without regard to match (96% of isolates did not match vaccine strains).1 100 233 In adults ≥50 years of age, antibody responses at 28 days after a single IM dose of trivalent influenza vaccine recombinant met predefined success criterion for all 3 vaccine antigens when compared with a single IM dose of trivalent influenza vaccine inactivated.1

  • Efficacy of influenza vaccines in preventing seasonal influenza virus infection depends on whether the virus strains represented in the vaccines are antigenically similar to influenza virus strains circulating during the influenza season.100 166 (See Limitations of Vaccine Effectiveness under Cautions.)

Advice to Patients

  • Prior to administration of seasonal influenza vaccine recombinant, provide a copy of the appropriate CDC Vaccine Information Statement (VIS) to the patient or patient's legal representative (VISs are available at ).1 477

  • Advise patient of the risks and benefits of vaccine administration.1

  • Advise patient that influenza vaccine recombinant contains noninfectious proteins that cannot cause influenza.1

  • Advise patient that annual vaccination against seasonal influenza is necessary.1 100 Importance of receiving a 2016–2017 seasonal influenza vaccine, even if the individual received a 2015–2016 seasonal influenza vaccine.100 112

  • Advise patient that influenza vaccine recombinant provides protection against illness due to influenza viruses represented in the vaccine and cannot provide protection against all respiratory illness.1

  • Importance of informing clinicians of any severe or life-threatening allergies, including any history of severe reaction after prior influenza vaccination.1

  • Importance of informing clinicians of adverse effects.1 Clinicians or individuals can report any adverse reactions that occur following vaccination to the Vaccine Adverse Event Reporting System (VAERS) at 800-822-7967 or .1 100

  • Importance of informing clinician of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as concomitant medical problems (e.g., Guillain-Barré syndrome).1

  • Importance of women informing clinician if they are or plan to become pregnant or plan to breast-feed.1

  • Importance of informing patients of other important precautionary information.1 (See Cautions.)


Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Influenza Vaccine Recombinant (2016–2017)


Dosage Forms


Brand Names



Injection, for IM use

45 mcg recombinant hemagglutinin each of A/California/7/2009 (H1N1), A/Hong Kong/4801/2014 (H3N2), and B/Brisbane/60/2008 per 0.5 mL


Protein Sciences

AHFS DI Essentials. © Copyright 2017, Selected Revisions November 8, 2016. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

† Use is not currently included in the labeling approved by the US Food and Drug Administration.


1. Protein Sciences Corporation. Flublok (influenza vaccine 2016–2017 formula) sterile solution for intramuscular injection prescribing information. Meriden; CT. 2016 Apr.

100. Grohskopf LA, Sokolow LZ, Broder KR et al. Prevention and Control of Seasonal Influenza with Vaccines. MMWR Recomm Rep. 2016; 65:1-54. [PubMed 27560619]

112. Committee on Infectious Diseases. Recommendations for Prevention and Control of Influenza in Children, 2016-2017. Pediatrics. 2016; :.

115. Centers for Disease Control and Prevention. CDC health information for international travel, 2016. Atlanta, GA: US Department of Health and Human Services. Updates may be available at CDC website.

134. National Center for Immunization and Respiratory Diseases. General recommendations on immunization --- recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2011; 60:1-64.

166. Centers for Disease Control and Prevention. Epidemiology and prevention of vaccine-preventable diseases. 13th ed. Washington DC: Public Health Foundation; 2015. Updates may be available at CDC website.

199. Centers for Disease Control and Prevention. Advisory Committee on Immunization Practices (ACIP) recommended immunization schedules for persons aged 0 through 18 years–United States, 2016. Updates may be available at CDC website.

200. Centers for Disease Control and Prevention. Advisory Committee on Immunization Practices (ACIP) recommended adult immunization schedule–United States, 2016. Updates may be available at CDC website.

233. Treanor JJ, El Sahly HM, King J, et al. Protective efficacy of a trivalent, insect cell-expressed, recombinant hemagglutinin protein vaccine (FluBlok) against culture confirmed influenza in healthy adults: a randomized, placebo-controlled trial. Vaccine. 2011; 29 (44): 7733-9. [PubMed 21835220]

234. Baxter R, Patriarca PA, Ensor K et al. Evaluation of the safety, reactogenicity and immunogenicity of FluBlok trivalent recombinant baculovirus-expressed hemagglutinin influenza vaccine administered intramuscularly to healthy adults 50-64 years of age. Vaccine. 2011; 29:2272-8. [PubMed 21277410]

235. Advisory Committee on Immunization Practices, Centers for Disease Control and Prevention (CDC). Immunization of health-care personnel: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2011; 60(RR-7):1-45.

470. US Food and Drug Administration. FDA approves first U.S. vaccine for humans against the avian influenza virus H5N1. April 19, 2007. From FDA web site.

477. Centers for Disease Control and Prevention. Influenza vaccine (flu vaccine, inactivated or recombinant) vaccine information statement. 2015 Aug 7. From CDC website.

567. Davlin SL, Blanton L, Kniss K et al. Influenza Activity - United States, 2015-16 Season and Composition of the 2016-17 Influenza Vaccine. MMWR Morb Mortal Wkly Rep. 2016; 65:567-75. [PubMed 27281364]

568. . Recommended composition of influenza virus vaccines for use in the 2016–2017 northern hemisphere influenza season. Wkly Epidemiol Rec. 2016; 91:121-32. [PubMed 26971356]