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Included as part of the PRECAUTIONS section.


Guillain-Barré Syndrome

The 1976 swine influenza vaccine was associated with an increased frequency of GBS. Evidence for a causal relation of GBS with other influenza vaccines is inconclusive; if an excess risk exists, it is probably slightly more than one additional case per 1 million persons vaccinated. If Guillain-Barré Syndrome (GBS) has occurred within 6 weeks of receipt of a prior influenza vaccine, the decision to give Flublok should be based on careful consideration of the potential benefits and risks.

Managing Allergic Reactions

Appropriate medical treatment and supervision must be available to manage possible anaphylactic reactions following administration of the vaccine.

Altered Immunocompetence

If Flublok is administered to immunocompromised individuals, including persons receiving immunosuppressive therapy, the immune response may be diminished.

Limitations of Vaccine Effectiveness

Vaccination with Flublok may not protect all vaccine recipients.

Patient Counseling Information

See FDA-approved patient labeling (PATIENT INFORMATION Sheet).

Inform the vaccine recipient of the potential benefits and risks of vaccination with Flublok.

Inform the vaccine recipient that:

  • Flublok contains non-infectious proteins that cannot cause influenza.
  • Flublok stimulates the immune system to produce antibodies that help protect against influenza viruses contained in the vaccine, but does not prevent other respiratory infections.

Instruct the vaccine recipient to report any adverse events to their healthcare provider and/or to the Vaccine Adverse Event Reporting System (VAERS).

Provide the vaccine recipient with the Vaccine Information Statements which are required by the National Childhood Vaccine Injury Act of 1986 to be given prior to vaccination. These materials are available free of charge at the Centers for Disease Control (CDC) website (

Inform the vaccine recipient that safety and efficacy have not been established in pregnant women. Register women who receive Flublok while pregnant in the pregnancy registry by calling 1-888-855-7871.

Instruct the vaccine recipient that annual vaccination to prevent influenza is recommended.

Nonclinical Toxicology

Flublok has not been evaluated for carcinogenic or mutagenic potential, or for impairment of male fertility in animals.

Reproduction studies performed in female rats revealed no evidence of impaired fertility due to Flublok (see Pregnancy).

Use In Specific Populations


Pregnancy Category B

Reproduction studies have been performed in rats at a dose approximately 300 times the human dose (on a mg/kg basis) and have revealed no evidence of impaired fertility or harm to the fetus due to Flublok. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this vaccine should be used during pregnancy only if clearly needed. The effect of Flublok on embryo-fetal and pre-weaning development was evaluated in pregnant rats. Animals were administered Flublok by intramuscular injection twice prior to gestation and once during the period of organogenesis (gestation days 6), 0.5 ml/rat/occasion (approximately 300-fold excess relative to the projected human dose on a mg/kg basis). No adverse effects on mating, female fertility, pregnancy, parturition, lactation, embryo-fetal and pre-weaning development were observed. There were no vaccine-related fetal malformations or other evidence of teratogenesis.

Nursing Mothers

Flublok has not been evaluated in nursing mothers. It is not known whether Flublok is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Flublok is administered to a nursing woman.

Pediatric Use

Data from a randomized, controlled study demonstrated that children 6 months to less than 3 years of age had diminished hemagglutinin inhibition (HAI) responses to Flublok as compared to a U.S.-licensed influenza vaccine approved for use in this population, strongly suggesting that Flublok would not be effective in children younger than 3 years of age. Safety and effectiveness of Flublok in children 3 years to less than 18 years of age have not been established.

Geriatric Use

The safety and effectiveness of Flublok have not been established in persons 50 years of age and older.

Last reviewed on RxList: 11/25/2013
This monograph has been modified to include the generic and brand name in many instances.


Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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