May 27, 2017
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"Everyone 6 months and older should get an annual flu vaccine. It takes about two weeks after vaccination for your body to develop full protection against the flu. Get vaccinated now to protect yourself and your loved ones!

Shorter days and "...





Included as part of the PRECAUTIONS section.


Managing Allergic Reactions

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

Guillain Barré Syndrome

The 1976 swine influenza vaccine was associated with an increased frequency of Guillain-Barré Syndrome (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 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.

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.

Nonclinical Toxicology

Flublok has not been evaluated for carcinogenic or mutagenic potential, or for impairment of male fertility in animals. A developmental toxicity study conducted in rats vaccinated with Flublok revealed no evidence of impaired female fertility (see Pregnancy).

Use In Specific Populations


Pregnancy Exposure

Pregnancy outcomes in women who have been exposed to Flublok during pregnancy are being monitored. Contact: Protein Sciences Corporation by calling 1-888-855-7871.

Risk Summary

All pregnancies have a risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risks of major birth defects and miscarriage in clinically recognized pregnancies are 2% to 4% and 15% to 20%, respectively. Available data on Flublok administered to pregnant women are insufficient to inform vaccine-associated risks in pregnant women.

A developmental study of Flublok has been performed in rats administered 0.5 mL (divided) of Flublok prior to mating and during gestation. This study revealed no evidence of harm to the fetus due to Flublok (see Data).

Clinical Considerations

Disease-associated Maternal and/or Embryo/Fetal Risk

Pregnant women are at increased risk of complications associated with influenza infection compared to non-pregnant women. Pregnant women with influenza may be at increased risk for adverse pregnancy outcomes, including preterm labor and delivery.



In a developmental toxicity study, female rats were administered 0.5 mL (divided) of Flublok by intramuscular injection twice prior to mating (35 days and 14 days prior to mating) and on gestation Day 6. No vaccine-related fetal malformations or variations and no adverse effects on pre-weaning development were observed in the study.


Risk Summary

It is not known whether Flublok is excreted in human milk. Data are not available to assess the effects of Flublok on the breastfed infant or on milk production/excretion.

The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for Flublok and any potential adverse effects on the breastfed child from Flublok or from the underlying maternal condition. For preventive vaccines, the underlying condition is susceptibility to disease prevented by the vaccine.

Pediatric Use

Data from a randomized, controlled trial demonstrated that children 6 months to less than 3 years of age had diminished hemagglutinin inhibition (HI) responses to Flublok 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 (6). Safety and effectiveness of Flublok have not been established in children 3 years to less than 18 years of age.

Geriatric Use

Data from an efficacy study (Study 6), which included 1759 subjects ≥ 65 years and 525 subjects ≥ 75 years who received Flublok Quadrivalent, are insufficient to determine whether elderly subjects respond differently from younger subjects (See Clinical Studies). The efficacy of Flublok Quadrivalent is relevant to Flublok (trivalent formulation) because both vaccines are manufactured using the same process and have overlapping compositions.

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 10/20/2016


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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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