Influenza Vaccine Recombinant (Monograph)

Brand name: Flublok
Drug class: Vaccines

Medically reviewed by Drugs.com on Dec 10, 2024. Written by ASHP.

Introduction

Recombinant influenza vaccine. Seasonal influenza vaccine recombinant (RIV; RIV3) contains recombinant hemagglutinin (HA) proteins representing influenza virus types A and type 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.

Uses for Influenza Vaccine Recombinant

Prevention of Seasonal Influenza A and B Virus Infections

Used to stimulate active immunity for prevention of disease caused by influenza virus subtypes A and B represented in the vaccine; FDA-labeled for use in adults ≥18 years of age.

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

ACIP and the American Academy of Pediatrics (AAP) provide recommendations and guidance for vaccination providers regarding the use of influenza vaccines in the US. These experts recommend routine influenza vaccination in all persons ≥6 months of age who do not have contraindications.

Seasonal influenza vaccination is particularly important for individuals at increased risk for severe influenza or influenza-related complications and those who live with or care for such individuals (e.g., health-care personnel, household or other close contacts).

All influenza vaccines available in the US for the 2024-25 season are trivalent formulations containing antigens representing influenza A (H1N1), influenza A (H3N2), and influenza B (Victoria lineage). For the 2024–25 influenza season, the influenza vaccine composition no longer includes influenza B/Yamagata because there have been no confirmed detections of influenza B/Yamagata viruses in global influenza surveillance since March 2020.

Various preparations of influenza virus vaccines are commercially available in the US. The vaccines can be grouped into 3 broad categories: inactivated influenza vaccines (IIV3), recombinant influenza vaccine (RIV3), and live attenuated virus vaccine (LAIV3). Inactivated influenza vaccines (IIV3) include standard-dose egg-based vaccines, a standard-dose cell culture-based influenza vaccine (ccIIV3), a high-dose egg-based vaccine (HD-IIV3), and an adjuvanted standard-dose egg-based vaccine (aIIV3).

ACIP states that all persons ≥6 months of age should receive an age-appropriate influenza vaccine with the exception of solid organ transplant recipients 18–64 years of age who are receiving immunosuppressive medication regimens; these individuals may receive either high-dose inactivated influenza vaccine (HD-IIV3) or adjuvanted inactivated influenza vaccine (aIIV3) as acceptable options (without a preference over other age-appropriate IIV3s or RIV3).

Because influenza vaccines are often less effective in older adults, the higher dose vaccines or adjuvanted vaccine is recommended in this population. For the 2024-25 influenza season, ACIP recommends that adults ≥65 years preferentially receive trivalent high-dose inactivated influenza vaccine (HD-IIV3), trivalent recombinant influenza vaccine (RIV3), or trivalent adjuvanted inactivated influenza vaccine (aIIV3). If none of these vaccines is available at an opportunity for vaccine administration, then any other age-appropriate influenza vaccine should be used.

With regard to timing of vaccine, for most individuals who need only 1 dose of influenza vaccine for the season, ACIP recommends that healthcare providers ideally offer influenza vaccination during September or October. However, vaccination should continue after October and throughout the influenza season as long as influenza viruses are circulating and unexpired vaccine is available. For most adults, vaccination during July and August generally should be avoided unless there is a concern that vaccination during the season might not be possible; however, vaccination during these months can be considered in children who require 2 doses, children who require only 1 dose but visit their healthcare provider during late summer before the start of the school year, and pregnant persons in the third trimester.

Influenza Vaccine Recombinant Dosage and Administration

General

Pretreatment Screening

Screen all individuals for contraindications and precautions to vaccination.

Dispensing and Administration Precautions

Appropriate medical treatment must be immediately available to manage potential anaphylactic reactions following administration of influenza vaccine recombinant.

Administration

Administer only by IM injection. Do not administer sub-Q, intradermally, or IV.

Syncope (vasovagal or vasodepressor reaction; fainting) may occur following vaccination; such reactions occur most frequently in adolescents and young adults. Take appropriate measures to decrease risk of injury if patient becomes weak or dizzy or loses consciousness (e.g., have vaccinees sit or lie down during and for 15 minutes after vaccination). If syncope occurs, observe patient until symptoms resolve.

May be given simultaneously with other age-appropriate vaccines. When multiple vaccines administered during a single health-care visit, give each parenteral vaccine using separate syringes and different injection sites. Separate injection sites by ≥1 inch (if anatomically feasible) to allow appropriate attribution of any local adverse effects that may occur.

IM Administration

Administer by IM injection preferably into the deltoid muscle in adults.

To ensure delivery into muscle, make IM injections at a 90° angle to the skin using a needle length appropriate for the individual’s age and body mass, thickness of adipose tissue and muscle at injection site, and injection technique.

Vaccine should appear clear and colorless; do not use if it appears discolored or contains particles.

Gently invert single-dose prefilled syringes of the vaccine prior to affixing appropriate size needle.

Do not mix with any other vaccine or solution.

Dosage

Adults

Prevention of Disease Caused by Seasonal Influenza A and B Virus Infections

Adults ≥18 Years of Age

Single 0.5-mL dose.

Special Populations

Geriatric Patients

Single 0.5-mL dose.

Cautions for Influenza Vaccine Recombinant

Contraindications

History of severe allergic reaction (e.g., anaphylaxis) to any component of the vaccine.
History of severe allergic reactions (e.g., anaphylaxis) to a previous dose of any recombinant influenza vaccine (quadrivalent or trivalent formulation).

Warnings/Precautions

Sensitivity Reactions

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

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

ACIP states a history of a severe allergic reaction (e.g., anaphylaxis) to any other influenza vaccine (i.e., any egg-based vaccine) is a precaution for the use of influenza vaccine recombinant. If the vaccine is administered in such an instance, vaccination should occur in an inpatient or outpatient medical setting and should be supervised by a healthcare provider who is able to recognize and manage severe allergic reactions. Although egg allergy is neither a contraindication nor precaution to the use of any influenza vaccine, there are contraindications and precautions related to allergies to vaccine components other than egg and to previous allergic reactions to influenza vaccines.

Guillain-Barré Syndrome (GBS)

If GBS has occurred within 6 weeks after previous influenza vaccination, the decision to administer influenza vaccine recombinant should be based on careful consideration of potential benefits and risks.

The 1976 swine influenza vaccine was associated with increased frequency of GBS. Evidence for causal relationship between other influenza vaccines and GBS inconclusive; if an excess risk exists, it probably is slightly more than 1 additional case of GBS per 1 million vaccinees.

ACIP states that a history of GBS within 6 weeks after receipt of any influenza vaccine is a precaution to the use of all influenza vaccines.

Individuals with Altered Immunocompetence

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

ACIP states that recombinant vaccines can be administered safely to individuals with altered immunocompetence.

Syncope

Syncope reported following vaccination. Procedures should be in place to avoid injury from fainting.

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.

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

Concomitant Illness

Base decision to administer or delay vaccination in an individual with a current or recent acute illness on severity of symptoms and etiology of the illness.

ACIP states mild acute illness generally does not preclude vaccination.

ACIP states moderate or severe acute illness (with or without fever) is a precaution for vaccination; defer vaccines until individual has recovered from the acute phase of the illness. This avoids superimposing vaccine adverse effects on the underlying illness or mistakenly concluding that a manifestation of the underlying illness resulted from vaccine administration.

Limitations of Vaccine Effectiveness

May not protect all vaccine recipients from influenza.

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. Efficacy of seasonal influenza vaccine during any given year depends on how closely viral strains represented in the vaccine match viral strains circulating during the season.

Specific Populations

Pregnancy

Manufacturer states data insufficient to assess risk of influenza vaccine recombinant in pregnant women.

Pregnant and postpartum women are at higher risk for severe influenza and complications from influenza, particularly during second and third trimesters.

Experts recommend vaccination against influenza in all women who are pregnant or who might become pregnant during the influenza season and state that any licensed, age-appropriate, inactivated influenza vaccine (i.e., influenza virus vaccine inactivated or influenza vaccine recombinant) can be used. These experts state that inactivated influenza vaccines can be administered at any time during pregnancy before or during influenza season. Encourage postpartum women who did not receive influenza vaccination during pregnancy to receive vaccination (e.g., before hospital discharge).

Pregnancy registry at 800-822-2463. Clinicians or vaccinees should report any exposure to the vaccine that occurs during pregnancy.

Lactation

Not known whether influenza vaccine recombinant is distributed into human milk. Data insufficient to assess effects on breast-fed infant or on milk production.

Consider benefits of breast-feeding and importance of the vaccine to the woman; also consider potential adverse effects on the breast-fed child from the vaccine or underlying maternal condition (i.e., susceptibility to influenza infection).

ACIP states recombinant vaccines do not pose any unusual risks for women who are breast-feeding or their breast-fed infants.

Pediatric Use

Safety and efficacy not established in individuals <18 years of age.

Geriatric Use

Insufficient experience using influenza vaccine recombinant in adults ≥65 years of age to determine whether geriatric patients respond differently than younger adults.

Common Adverse Effects

In adults 18 through 49 years of age, most common (≥10%) injection-site adverse reaction was pain (37%); most common (≥10%) solicited systemic adverse reactions were headache (15%), fatigue (15%), and muscle pain (11%).

In adults 50 through 64 years of age, most common (≥10%) injection site adverse reaction was pain (32%); most common (≥10%) solicited systemic adverse reactions were headache (17%), fatigue (13%), and muscle pain (11%).

In adults 65 years of age and older, most common (≥10%) injection site adverse reaction was pain (19%); most common (≥10%) solicited systemic adverse reactions were fatigue (13%) and headache (10%).

Drug Interactions

Immunosuppressive Agents

Immune responses to vaccines may be reduced in individuals receiving immunosuppressive agents.

Generally, give inactivated vaccines ≥2 weeks prior to initiation of immunosuppressive therapy and, because of possible suboptimal response, do not give during and for certain periods of time after immunosuppressive therapy discontinued.

Time to restoration of immune competence varies depending on type and intensity of immunosuppressive therapy, underlying disease, and other factors; optimal timing for vaccine administration after discontinuance of immunosuppressive therapy not identified for every situation.

Vaccines

Although specific studies may not be available, ACIP states influenza vaccine recombinant may be administered concurrently or sequentially with other age-appropriate vaccines, including live virus vaccines, toxoids, or inactivated or recombinant vaccines.

Specific Drugs

Drug

Interaction

Comments

Antivirals active against influenza (baloxavir, oseltamivir, peramivir, zanamivir)

No effect on immune response to inactivated vaccines, including influenza vaccine recombinant

Influenza vaccine recombinant may be given to individuals receiving an influenza antiviral

COVID-19 vaccines

Controlled studies did not identify evidence of safety concerns or any evidence of immune interference on influenza hemagglutination inhibition or SARS-CoV-2 binding antibody responses

Some studies report similar incidence of local reactions, but slightly increased systemic reactions, especially with high dose or adjuvant-containing vaccines

Influenza vaccine recombinant may be administered concurrently with or at any interval before or after COVID-19 vaccines

Base decisions to administer a COVID-19 vaccine concomitantly with other vaccine(s) on whether routine vaccination with the other vaccines has been delayed or missed, the individual's risk of vaccine-preventable disease (e.g., during an outbreak or occupational exposures), and reactogenicity profiles of the vaccines

Respiratory Syncytial Virus Vaccines

Concomitant administration with seasonal influenza vaccines met noninferiority criteria for immunogenicity with the exception of the FluA/Darwin H3N2 strain when the GSK RSV vaccine was administered concomitantly with adjuvanted quadrivalent inactivated influenza vaccine. RSV and influenza antibody titers were somewhat lower with concomitant administration; however, the clinical significance of this is unknown.

ACIP states that concomitant administration of RSV vaccines with other adult vaccines during the same visit is acceptable, but might increase local or systemic reactogenicity.

Stability

Storage

Parenteral

Injectable Solution, for IM Use

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

Protect from light.

Does not contain thimerosal or any other preservatives.

Actions

Influenza vaccine recombinant contains recombinant hemagglutinin (HA) proteins from suitable strains of influenza viruses. 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. Manufacturing process does not involve live influenza viruses and does not involve eggs.
Seasonal influenza vaccines are formulated annually to contain antigens representative of the influenza A (H1N1), influenza A (H3N2), and influenza B virus likely to circulate during the upcoming influenza season.
Influenza vaccines stimulate active immunity to influenza virus strains represented in the vaccines.
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.
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.

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.
Advise patient of the risks and benefits of influenza vaccine recombinant.
Advise patient that influenza vaccine recombinant contains noninfectious proteins that cannot cause influenza.
Advise patient that annual vaccination against seasonal influenza is necessary. Stress importance of receiving influenza vaccine for the upcoming (current) influenza season, even if the individual received influenza vaccine for the previous influenza season.
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.
Stress importance of informing clinicians of any severe or life-threatening allergies, including any history of severe reaction after prior influenza vaccination.
Stress importance of informing clinicians of adverse effects. 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 [Web].
Stress importance of informing clinician of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as concomitant illnesses (e.g., GBS).
Stress importance of women informing clinician if they are or plan to become pregnant or plan to breast-feed.
Inform patients of other important precautionary information.

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Preparations

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
Routes	Dosage Forms	Strengths	Brand Names	Manufacturer
Parenteral	Injection, for IM use	45 mcg recombinant hemagglutinin each of FDA-specified influenza A (H1N1), influenza A (H3N2), and influenza B/Victoria lineage antigens per 0.5 mL	Flublok	Sanofi Pasteur