6.2 Post-Marketing Experience

The following events have been spontaneously reported during the post-approval use of Fluzone (trivalent) or Fluzone Quadrivalent Southern Hemisphere. Because these events are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to vaccine exposure. Adverse events were included based on one or more of the following factors: severity, frequency of reporting, or strength of evidence for a causal relationship to Fluzone (trivalent) or Fluzone Quadrivalent Southern Hemisphere.

  • Blood and Lymphatic System Disorders: Thrombocytopenia, lymphadenopathy
  • Immune System Disorders: Anaphylaxis, other allergic/hypersensitivity reactions (including urticaria, angioedema)
  • Eye Disorders: Ocular hyperemia
  • Nervous System Disorders: Guillain-Barré syndrome (GBS), convulsions, febrile convulsions, myelitis (including encephalomyelitis and transverse myelitis), facial palsy (Bell’s palsy), optic neuritis/neuropathy, brachial neuritis, syncope (shortly after vaccination), dizziness, paresthesia
  • Vascular Disorders: Vasculitis, vasodilatation/flushing
  • Respiratory, Thoracic and Mediastinal Disorder s: Dyspnea, cough, wheezing, throat tightness, oropharyngeal pain, rhinorrhea
  • Skin and Subcutaneous Tissue Disorders: Rash, pruritus, and Stevens-Johnson syndrome
  • General Disorders and Administration Site Conditions: Asthenia/fatigue, pain in extremities, chest pain
  • Gastrointestinal Disorders: Vomiting


Fluzone Quadrivalent Southern Hemisphere and Fluzone Quadrivalent are manufactured using the same process. Data in this section were obtained in studies with Fluzone Quadrivalent.

8.1 Pregnancy

Pregnancy Exposure Registry

Sanofi Pasteur Inc. is maintaining a prospective pregnancy exposure registry to collect data on pregnancy outcomes following vaccination with Fluzone Quadrivalent during pregnancy. Healthcare providers are encouraged to enroll women who receive Fluzone Quadrivalent during pregnancy in Sanofi Pasteur Inc.’s vaccination pregnancy registry by calling 1-800-822-2463.

Risk Summary

All pregnancies have a risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

Available data with Fluzone Quadrivalent use in pregnant women are insufficient to inform vaccine-associated risk of adverse developmental outcomes.

A developmental and reproductive toxicity study was performed in female rabbits given a 0.5 mL/dose of Fluzone Quadrivalent prior to mating and during gestation (a single human dose is 0.5 mL). This study revealed no adverse effects to the fetus or pre-weaning development due to Fluzone Quadrivalent [see Animal Data (8.1)].


Animal Data: In a developmental and reproductive toxicity study female rabbits were administered a 0.5 mL/dose of Fluzone Quadrivalent by intramuscular injection 24 and 10 days before insemination, and on Days 6, 12, and 27 of gestation (a single human dose is 0.5 mL). There were no adverse effects on pre-weaning development or vaccine-related fetal malformations noted in this study.

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 who contract influenza may be at increased risk for adverse pregnancy outcomes, including preterm labor and delivery.

8.2 Lactation

Risk Summary

It is not known whether Fluzone Quadrivalent is excreted in human milk. Data are not available to assess the effects of Fluzone Quadrivalent 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 Fluzone Quadrivalent and any potential adverse effects on the breastfed child from Fluzone Quadrivalent or from the underlying maternal condition. For preventive vaccines, the underlying maternal condition is susceptibility to the disease prevented by the vaccine.

8.4 Pediatric Use

Safety and effectiveness of Fluzone Quadrivalent Southern Hemisphere in children below the age of 6 months have not been established.

8.5 Geriatric Use

Safety and immunogenicity of Fluzone Quadrivalent were evaluated in adults 65 years of age and older. [See Clinical Studies (14.6).] Antibody responses to Fluzone Quadrivalent are lower in persons ≥65 years of age than in younger adults.


Fluzone Quadrivalent Southern Hemisphere (Influenza Vaccine) for intramuscular injection is an inactivated influenza vaccine, prepared from influenza viruses propagated in embryonated chicken eggs. The virus- containing allantoic fluid is harvested and inactivated with formaldehyde. Influenza virus is concentrated and purified in a linear sucrose density gradient solution using a continuous flow centrifuge. The virus is then chemically disrupted using a non-ionic surfactant, octylphenol ethoxylate (Triton® X-100), producing a “split virus”. The split virus is further purified and then suspended in sodium phosphate-buffered isotonic sodium chloride solution. The Fluzone Quadrivalent process uses an additional concentration factor after the ultrafiltration step in order to obtain a higher hemagglutinin (HA) antigen concentration. Antigens from the four strains included in the vaccine are produced separately and then combined to make the quadrivalent formulation.

Fluzone Quadrivalent Southern Hemisphere suspension for injection is clear and slightly opalescent in color.

Antibiotics are not used in the manufacture of Fluzone Quadrivalent Southern Hemisphere.

The Fluzone Quadrivalent Southern Hemisphere prefilled syringe and vial presentations are not made with natural rubber latex.

Fluzone Quadrivalent Southern Hemisphere is standardized according to United States Public Health Service requirements and is formulated to contain HA of each of the following four influenza strains recommended for the 2023 Southern Hemisphere influenza season: A/Sydney/5/2021 SAN-013 (H1N1), A/Darwin/9/2021 SAN-010 (H3N2), B/Phuket/3073/2013 (B Yamagata lineage), and B/Michigan/01/2021 (a B/Austria/1359417/2021-like virus, B Victoria lineage). The amounts of HA and other ingredients per dose of vaccine are listed in Table 7. The single-dose, pre-filled syringe (0.5 mL) is formulated without thimerosal or any other preservative. The 5 mL multi-dose vial presentation contains thimerosal, a mercury derivative, added as a preservative. Each 0.5 mL dose from the multi-dose vial contains 25 mcg mercury. Each 0.25 mL dose from the multi-dose vial contains 12.5 mcg mercury.

Table 7: Fluzone Quadrivalent Southern Hemisphere Ingredients
Ingredient Quantity (per dose)
Fluzone Quadrivalent0.25 mL Dose Fluzone Quadrivalent0.5 mL Dose
“-” Indicates information is not applicable
per United States Public Health Service recommendations
Quantity Sufficient
Active Substance: Split influenza virus, inactivated strains *: 30 mcg HA total 60 mcg HA total
A (H1N1) 7.5 mcg HA 15 mcg HA
A (H3N2) 7.5 mcg HA 15 mcg HA
B/(Victoria lineage) 7.5 mcg HA 15 mcg HA
B/(Yamagata lineage) 7.5 mcg HA 15 mcg HA
Sodium phosphate-buffered isotonic sodium chloride solution QS to appropriate volume QS to appropriate volume
Formaldehyde ≤50 mcg ≤100 mcg
Octylphenol ethoxylate ≤125 mcg ≤250 mcg
Single-dose presentations
Multi-dose presentation (thimerosal) 12.5 mcg mercury 25 mcg mercury


12.1 Mechanism of Action

Influenza illness and its complications follow infection with influenza viruses. Global surveillance of influenza identifies yearly antigenic variants. Since 1977, antigenic variants of influenza A (H1N1 and H3N2) viruses and influenza B viruses have been in global circulation. Since 2001, two distinct lineages of influenza B (Victoria and Yamagata lineages) have co-circulated worldwide. Protection from influenza virus infection has not been correlated with a specific level of hemagglutination inhibition (HI) antibody titer post-vaccination. However, in some human studies, antibody titers ≥1:40 have been associated with protection from influenza illness in up to 50% of subjects. (See ref. 2) (See ref. 3)

Antibodies against one influenza virus type or subtype confer limited or no protection against another. Furthermore, antibodies to one antigenic variant of influenza virus might not protect against a new antigenic variant of the same type or subtype. Frequent development of antigenic variants through antigenic drift is the virologic basis for seasonal epidemics and the reason for the usual change of one or more new strains in each year’s influenza vaccine. Therefore, influenza vaccines are standardized to contain the hemagglutinins of influenza virus strains representing the influenza viruses likely to be circulating during the influenza season in the hemisphere for which the vaccine is intended.

Annual vaccination with the influenza vaccine is recommended because immunity during the year after vaccination declines and because circulating strains of influenza virus change from year to year. provides trustworthy package insert and label information about marketed drugs and vaccines as submitted by manufacturers to the U.S. Food and Drug Administration. Package information is not reviewed or updated separately by Every individual vaccine label and package insert entry contains a unique identifier which can be used to secure further details directly from the U.S. National Institutes of Health and/or the FDA.

Vaccine Sections

Vaccine Information by RSS

As the leading independent provider of trustworthy vaccine information, our database comes directly from the FDA's central repository of drug labels and package inserts under the Structured Product Labeling standard. provides the full vaccine subset of the FDA's repository. Vaccine information provided here is not intended as a substitute for direct consultation with a qualified health professional.

Terms of Use | Copyright © 2023. All Rights Reserved.