Designed to produce an exact match to the WHO-selected strains.4,6

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Key Features
  • Efficacy of FLUCELVAX QUADRIVALENT was demonstrated in children and adolescents 2 through 17 years1
  • Demonstrated safety profile in patients 6 months and older1
  • Proven noninferior to a US-licensed comparator quadrivalent influenza vaccine for patients 6 months through 3 years based on data demonstrating immunogenicity and seroconversion1
  • Proven noninferior to FLUCELVAX® (Influenza Vaccine) for patients 4 through 17 years based on data demonstrating immunogenicity and seroconversion1
  • Proven noninferior to FLUCELVAX in adults 18 years and older based on data demonstrating immunogenicity and seroconversion1
  • Free of eggs and antibiotics1
  • 0.5-mL pre-filled syringes contain no preservative; 5-mL multi-dose vials contain thimerosal, a mercury derivative, added as a preservative1

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Clinical Data
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FLUCELVAX® QUADRIVALENT helps prevent seasonal influenza in patients 6 months and older.1

FLUCELVAX QUADRIVALENT (Influenza Vaccine) was proven noninferior to a US-licensed comparator quadrivalent influenza vaccine for patients 6 months through 3 years (Study 1) and noninferior to FLUCELVAX (Influenza Vaccine) for patients 4 through 17 years (Study 5) based on data demonstrating immunogenicity and seroconversion.

Efficacy of FLUCELVAX QUADRIVALENT against culture and/or RT-PCR-confirmed influenza was demonstrated in a clinical study over 3 influenza seasons (Study 2).*1

VACCINE EFFICACY OF FLUCELVAX QUADRIVALENT IN THOSE 2 THROUGH 17 YEARS*1

*Absolute efficacy of FLUCELVAX QUADRIVALENT was evaluated in Study 2, a multinational, randomized, observer-blind, non-influenza vaccine comparator-controlled study during the following 3 influenza seasons: Southern Hemisphere 2017, Northern Hemisphere 2017-2018, and Northern Hemisphere 2018-2019. A total of 4513 children and adolescents 2 through 17 years received FLUCELVAX QUADRIVALENT (N=2258) or a non-influenza (meningococcal [Groups A, C, Y, and W-135] oligosaccharide diphtheria CRM197 conjugate) comparator vaccine (N=2255). Children 2 through 8 years of age received either 1 or 2 doses (separated by 4 weeks) of FLUCELVAX QUADRIVALENT or comparator vaccine depending on the subject's prior influenza vaccination history. Children in the 2-dose comparator group received non-influenza comparator as the first dose and saline placebo as the second dose. Children and adolescents 9 through 17 years of age received a single dose of FLUCELVAX QUADRIVALENT or non-influenza comparator vaccine. The full analysis set (FAS) for efficacy consisted of 4509 children and adolescents. FLUCELVAX QUADRIVALENT met the pre-defined success criterion defined as the lower limit of the 2-sided 95% CI of absolute vaccine efficacy greater than 20%. Antigenically matched, culture-confirmed influenza 95% CI: 53.6-71.5; culture-confirmed influenza 95% CI: 51.3-68.5; RT-PCR or culture-confirmed influenza 95% CI: 45.7-62.1.1

FLUCELVAX QUADRIVALENT (Influenza Vaccine) was proven noninferior to FLUCELVAX in adults 18 years and older (Study 3) based on data demonstrating on immunogenicity and seroconversion.1

The efficacy data of FLUCELVAX are relevant to FLUCELVAX QUADRIVALENT, as both vaccines are manufactured using the same process and have overlapping compositions.1

DEMONSTRATED EFFICACY OF FLUCELVAX (Influenza Vaccine) AGAINST CULTURE-CONFIRMED INFLUENZA IN THOSE 18 THROUGH 49 YEARS†1

†A multinational, randomized, observer-blind, placebo-controlled trial was performed to assess clinical efficacy and safety of FLUCELVAX during the 2007-2008 influenza season in adults aged 18 through 49 years (Study 4). A total of 11,404 adults were enrolled to receive FLUCELVAX (N=3828), AGRIFLU (N=3676), or placebo (N=3900) in a 1:1:1 ratio. FLUCELVAX met the pre-defined success criterion defined as the lower limit of the 1-sided 97.5% CI for the estimate of the vaccine efficacy relative to placebo >40%. Antigenically matched influenza lower limit of the 1-sided 97.5% CI: 61.0; all culture-confirmed influenza lower limit of the 1-sided 97.5% CI: 55.0.1

Safety Data
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DEMONSTRATED SAFETY PROFILE IN CHILDREN AND ADOLESCENTS 6 MONTHS THROUGH 17 YEARS

The safety of FLUCELVAX QUADRIVALENT was evaluated in children and adolescents in two clinical studies, Studies 1 and 2.1

MOST COMMON (≥10%) LOCAL AND SYSTEMIC ADVERSE REACTIONS OBSERVED IN CHILDREN WITHIN 7 DAYS OF FIRST DOSE OF VACCINATION†1

*Study 1 was a randomized, observer-blind, multicenter study in children 6 months through 3 years of age. The solicited safety population consisted of 2348 subjects who received FLUCELVAX QUADRIVALENT (N=1564) or a US-licensed quadrivalent influenza vaccine comparator (N=784).4

†Study 2 was a multiseason, multinational, randomized, observer-blind study in children 2 through 17 years of age. The solicited safety population included a total of 4509 children and adolescents 2 through 17 years of age who received FLUCELVAX QUADRIVALENT (N=2255) or a non-influenza comparator vaccine (N=2254)4

DEMONSTRATED SAFETY PROFILE IN ADULTS 18 YEARS AND OLDER

FLUCELVAX® QUADRIVALENT has a demonstrated safety profile similar to comparator trivalent vaccines (TIV1c or TIV2c).1

MOST COMMON (≥10%) LOCAL AND SYSTEMIC ADVERSE REACTIONS OBSERVED IN ADULTS WITHIN 7 DAYS OF VACCINATION‡1

‡The immunogenicity and safety of FLUCELVAX QUADRIVALENT in adults 18 years and older was evaluated in Study 1, a randomized, double-blind, controlled study conducted in the US (Study 1). In this study, adults received FLUCELVAX QUADRIVALENT or 1 of 2 FLUCELVAX trivalent formulations (FLUCELVAX QUADRIVALENT, N=1334, TIV1c, N=677, or TIV2c, N=669). The safety population included a total of 2680 adults 18 years of age and older; 1340 adults 18 through 64 years of age; and 1340 adults 65 years of age and older. The immunogenicity endpoints were the percentage of adults who achieved seroconversion and the percentage of adults with a postvaccination HI titer ≥1:401

Dosing and Administration
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For intramuscular injection only.1

Administer FLUCELVAX QUADRIVALENT as a 0.5-mL dose for people 6 months and older.*1

FLUCELVAX QUADRIVALENT is supplied in 2 product presentations: as a package of ten 0.5-mL pre-filled, needleless syringes and as a 5-mL multi-dose vial.1

FLUCELVAX QUADRIVALENT contains no egg protein and no antibiotics.1

*1 or 2 doses depends on vaccination history as per Advisory Committee on Immunization Practices annual recommendations on prevention and control of influenza with vaccines

Storage and Handling
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Store FLUCELVAX QUADRIVALENT refrigerated at 2 °C to 8 °C (36 °F to 46 °F). Protect from light. Do not freeze. Discard if the vaccine has been frozen. Do not use after expiration date.1

RWE studies support the clinical effectiveness of FLUCELVAX QUADRIVALENT for a more complete picture7-17

There's more to understanding a vaccine's potential than clinical trial data alone. Since influenza varies each year, look to both clinical trial and real-world evidence (RWE) data when considering an influenza vaccine.18,19

In seasons where egg adaptation occurs, studies suggest FLUCELVAX QUADRIVALENT has the potential to be more effective than traditional, egg-based vaccines.7-17 The outcomes reported in these publications contain information not included in the Prescribing Information.

Flucelvax Quadrivalent vs standard-dose, egg-based influenza vaccines
These studies provide RWE data across 3 US influenza seasons with different study designs, outcomes, and study limitations comparing the relative vaccine effectiveness (rVE) of FLUCELVAX QUADRIVALENT compared to traditional, egg-based influenza vaccines.7-17
STUDY 1
8% fewer laboratory-confirmed influenza A illnesses with FLUCELVAX QUADRIVALENT*7
(rVE 8%; 95% CI -10, 23)
40% fewer laboratory-confirmed influenza B illnesses with FLUCELVAX QUADRIVALENT*7
(rVE 39.6%; 95% CI 27.9, 49.3)
Design: Retrospective cohort study, 803,813 (influenza B) to over 1 million (influenza A) persons 4-64 years, US 2017-2018 season†
Limitations: Low proportion of vaccines received QIVc, limiting study power; potential for bias if providers preferentially gave either vaccine to higher-risk individuals
STUDY 2
No difference in the relative VE for laboratory-confirmed influenza vs. SDe8
(rVE 0%; 95% CI -30, 20)‡
Design: Test-negative case-control study, 1508 DoD healthcare beneficiaries ≥6 months, US 2017-2018 season†
Limitations: Due to a limited supply of vaccine, the DoD asked persons ≥9 years to receive QIVc; results did not account for comorbidities and health status
STUDY 3
15% fewer laboratory-confirmed influenza hospitalizations with FLUCELVAX QUADRIVALENT9
(rVE 15%; 95% CI -26, 43)
Design: Test-negative case-control study, 5471 persons ≥4 years, US 2017-2018 season†
Limitations: Results did not account for all residual confounding (eg, frailty); selection bias in hospitalizations and testing
STUDY 4
36% fewer influenza-like illnesses within a primary care setting with FLUCELVAX QUADRIVALENT10
(rVE 36.2%; 95% CI 26.1, 44.9)
Design: Retrospective cohort study, over 1.3 million persons ≥4 years, US 2017-2018 season
Limitations: Results were not adjusted by unmeasurable confounders; inability to reliably estimate absolute influenza VE from the ambulatory EMR dataset
STUDY 5
14% fewer influenza-related hospitalizations or ER visits with FLUCELVAX QUADRIVALENT11
(rVE 14.4%; 95% CI 8.8, 19.6)
Design: Retrospective cohort study, over 3 million persons 4-64 years, US 2017-2018 season
Limitations: Results were not adjusted by unmeasurable confounders; findings may not be representative of uninsured, Medicaid, or Medicare populations
STUDY 6
11% fewer influenza-related hospital encounters with FLUCELVAX QUADRIVALENT12
(rVE 11%; 95% CI 7.9, 14)
Design: Retrospective cohort study, over 2.5 million adults ≥65 years, US 2017-2018 season
Limitations: Potential for residual confounding; Medicare claims may not be representative of private or uninsured populations
STUDY 1
3% fewer influenza-related hospitalizations or ER visits with FLUCELVAX QUADRIVALENT13
(rVE 2.5%; 95% CI -2.4, 7.3)
Design: Retrospective cohort study, over 2.2 million adults ≥65 years, US 2018-2019 season
Limitations: Potential for residual confounding; lack of laboratory confirmation
STUDY 2
7% fewer influenza-related hospitalizations or ER visits with FLUCELVAX QUADRIVALENT14
(rVE 6.5%; 95% CI 0.1, 12.5)
Design: Retrospective cohort study, over 3.7 million persons 4-64 years, US 2018-2019 season
Limitations: Results were not adjusted by unmeasurable confounders; findings may not be representative of uninsured, Medicaid, or Medicare populations
STUDY 3
8% fewer influenza-related medical encounters with FLUCELVAX QUADRIVALENT15
(rVE 7.6%; 95% CI 6.5, 8.6)
Design: Retrospective cohort study, over 10.1 million adults ≥65 years, US 2018-2019 season
Limitations: Analyses did not specifically adjust for frailty; unmeasured confounding is a potential source of bias
STUDY 1
3% fewer influenza-related hospital encounters with FLUCELVAX QUADRIVALENT16
(rVE 2.8%; 95% CI -2.8, 8.2)
Design: Retrospective cohort study, over 2.4 million adults ≥65 years, US 2019-2020 season
Limitations: Potential for residual confounding; lack of laboratory confirmation
STUDY 2
5% fewer influenza-related hospitalizations or ER visits with FLUCELVAX QUADRIVALENT17
(rVE 5.3%; 95% CI 0.5, 9.9)
Design: Retrospective cohort study, over 2.4 million adults ≥65 years, US 2019-2020 season
Limitations: Potential for residual confounding; lack of laboratory confirmation

*These results are from the same study. The rVE for influenza A compared QIVc to both TIVe and QIVe and the rVE for influenza B compared QIVc to TIVe only

†There was also an unvaccinated arm in this study

‡rVE calculated as (1-adjusted odds ratio) x 100

CI=confidence interval; DoD=Department of Defense; QIVc=cell-based, quadrivalent influenza vaccine; QIVe=egg-based, quadrivalent influenza vaccine; rVE=relative vaccine effectiveness; SDe=standard-dose, egg-based vaccines; TIVe=egg-based, trivalent influenza vaccine; VE=vaccine effectiveness

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A brochure designed to educate patients about vaccination with FLUCELVAX QUADRIVALENT (Influenza Vaccine).

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FLUCELVAX® QUADRIVALENT Patient Brochure

Educate patients about vaccination with FLUCELVAX QUADRIVALENT (Influenza Vaccine).

A flashcard highlighting the features of FLUCELVAX QUADRIVALENT (Influenza Vaccine)

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FLUCELVAX® QUADRIVALENT Informational Flyer

Key information highlighting the features of FLUCELVAX QUADRIVALENT (Influenza Vaccine).

Flyer that highlights FLUCELVAX QUADRIVALENT and its clinical effectiveness for patients 6+ months.

FLUCELVAX QUADRIVALENT | CLINICAL

FLUCELVAX® QUADRIVALENT Real-World Evidence (RWE) Studies

See the RWE of FLUCELVAX QUADRIVALENT (Influenza Vaccine) over multiple seasons for a more complete picture of how it may impact influenza-related clinical outcomes.

Influenza impacts millions of people in the US

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Please see Important Safety Information and full US Prescribing Information on each vaccine's respective product page.

INDICATION AND IMPORTANT SAFETY INFORMATION

IMPORTANT SAFETY INFORMATION

CONTRAINDICATIONS

Do not administer FLUAD QUADRIVALENT or AFLURIA QUADRIVALENT to anyone with a history of severe allergic reaction (e.g. anaphylaxis) to any component of the vaccine, including egg protein, or to a previous influenza vaccine.

Do not administer FLUCELVAX QUADRIVALENT to anyone with a history of severe allergic reactions (e.g. anaphylaxis) to any component of the vaccine.

WARNINGS AND PRECAUTIONS

If Guillain-Barré syndrome (GBS) has occurred within 6 weeks of receipt of prior influenza vaccine, the decision to give FLUAD QUADRIVALENT, FLUCELVAX QUADRIVALENT, or AFLURIA QUADRIVALENT should be based on careful consideration of the potential benefits and risks.

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

Syncope (fainting) may occur in association with administration of injectable vaccines. Syncope can be accompanied by transient neurological signs such as visual disturbance, paresthesia, and tonic-clonic limb movements. Ensure procedures are in place to avoid falling injury and to restore cerebral perfusion following syncope by maintaining a supine or Trendelenburg position.

The immune response to FLUAD QUADRIVALENT, FLUCELVAX QUADRIVALENT, or AFLURIA QUADRIVALENT in immunocompromised persons, including individuals receiving immunosuppressive therapy, may be lower than in immunocompetent individuals.

Vaccination with FLUAD QUADRIVALENT, FLUCELVAX QUADRIVALENT, or AFLURIA QUADRIVALENT may not protect all vaccine recipients against influenza disease.

ADVERSE REACTIONS

FLUAD QUADRIVALENT:

The most common (≥ 10%) local and systemic reactions with FLUAD QUADRIVALENT in elderly subjects 65 years of age and older were injection site pain (16.3%), headache (10.8%) and fatigue (10.5%). Other adverse events may occur.

FLUCELVAX QUADRIVALENT:

In children 6 months through 3 years of age who received FLUCELVAX QUADRIVALENT, the most commonly reported injection-site adverse reactions were tenderness (27.9%), erythema (25.8%), induration (17.3%) and ecchymosis (10.7%). The most common systemic adverse reactions were irritability (27.9%), sleepiness (26.9%), diarrhea (17.9%) and change of eating habits (17.4%).

In children 2 through 8 years of age who received FLUCELVAX QUADRIVALENT, the most commonly reported injection-site adverse reactions were tenderness (28.7%), pain (27.9%) and erythema (21.3%), induration (14.9%) and ecchymosis (10.0%). The most common systemic adverse reactions were sleepiness (14.9%), headache (13.8%), fatigue (13.8%), irritability (13.8%) and loss of appetite (10.6%).

In children and adolescents 9 through 17 years of age who received FLUCELVAX QUADRIVALENT, the most commonly reported injection-site adverse reactions were injection site pain (21.7%), erythema (17.2%) and induration (10.5%). The most common systemic adverse reactions were headache (18.1%) and fatigue (17.0%).

In adults 18 through 64 years of age who received FLUCELVAX QUADRIVALENT, the most commonly reported injection-site adverse reactions were pain (45.4%), erythema (13.4%) and induration (11.6%). The most common systemic adverse reactions were headache (18.7%), fatigue (17.8%) and myalgia (15.4%).

In adults ≥65 years of age who received FLUCELVAX QUADRIVALENT, the most commonly reported injection-site adverse reactions were pain (21.6%) and erythema (11.9%).

Other adverse events may occur.

AFLURIA QUADRIVALENT:

AFLURIA QUADRIVALENT administered by needle and syringe:

In children 6 months through 35 months of age, the most frequently reported injection site reactions in the clinical study with AFLURIA QUADRIVALENT administered by needle and syringe were pain and redness (≥ 20%). The most common systemic adverse events were irritability (≥ 30%), diarrhea and loss of appetite (≥ 20%).

In children 36 through 59 months of age, the most commonly reported injection site reactions in the clinical study with AFLURIA QUADRIVALENT administered by needle and syringe were pain (≥ 30%) and redness (≥ 20%). The most commonly reported systemic adverse events were malaise and fatigue, and diarrhea (≥ 10%).

In children 5 through 8 years, the most commonly reported injection-site adverse reactions when AFLURIA QUADRIVALENT was administered by needle and syringe were pain (≥ 50%), redness and swelling (≥ 10%). The most common systemic adverse event was headache (≥ 10%).

In children 9 through 17 years, the most commonly reported injection-site adverse reactions when AFLURIA QUADRIVALENT was administered by needle and syringe were pain (≥ 50%), redness and swelling (≥ 10%). The most common systemic adverse events were headache, myalgia, and malaise and fatigue (≥ 10%).

In adults 18 through 64 years of age, the most commonly reported injection-site adverse reaction observed in clinical studies with AFLURIA QUADRIVALENT administered by needle and syringe was pain (≥ 40%). The most common systemic adverse events observed were myalgia and headache (≥ 20%).

In adults 65 years of age and older, the most commonly reported injection-site adverse reaction observed in clinical studies with AFLURIA QUADRIVALENT administered by needle and syringe was pain (≥ 20%). The most common systemic adverse event observed was myalgia (≥ 10%).

AFLURIA (trivalent formulation) administered by PharmaJet Stratis Needle-Free Injection System:

The safety experience with AFLURIA (trivalent formulation) is relevant to AFLURIA QUADRIVALENT because both vaccines are manufactured using the same process and have overlapping compositions.

In adults 18 through 64 years of age, the most commonly reported injection-site adverse reactions observed in a clinical study with AFLURIA (trivalent formulation) using the PharmaJet Stratis Needle-Free Injection System were tenderness (≥ 80%), swelling, pain, redness (≥ 60%), itching (≥ 20%) and bruising (≥ 10%). The most common systemic adverse events were myalgia, malaise (≥ 30%) and headache (≥ 20%).

Other adverse events may occur.

To report SUSPECTED ADVERSE REACTIONS, contact CSL Seqirus at 1-855-358-8966 or VAERS at 1-800-822-7967 or www.vaers.hhs.gov.

Before administration, please see the full US Prescribing Information for FLUAD QUADRIVALENT, FLUCELVAX QUADRIVALENT and AFLURIA QUADRIVALENT.

FLUAD® QUADRIVALENT, FLUCELVAX® QUADRIVALENT, AFLURIA® and AFLURIA® QUADRIVALENT are registered trademarks of Seqirus UK Limited or its affiliates.

PharmaJet® and STRATIS® are registered trademarks of PharmaJet.

References:

1. FLUCELVAX QUADRIVALENT. Package insert. Seqirus Inc; 2022. 2. Data on file. Seqirus Inc; 2022. 3. Medicare.gov. Flu shots. Accessed September 13, 2022. https://www.medicare.gov/coverage/flu-shots 4. Rajaram S, Boikos C, Gelone DK, Gandhi A. Influenza vaccines: the potential benefits of cell-culture isolation and manufacturing. Ther Adv Vaccines Immunother. 2020;8:2515135520908121. doi:10.1177/2515135520908121 5. Centers for Disease Control and Prevention. Cell-based flu vaccines. Accessed September 22, 2022. https://www.cdc.gov/flu/prevent/cell-based.htm 6. Mabrouk T, Ellis RW. Influenza vaccine technologies and the use of the cell-culture process (cell-culture influenza vaccine). Dev Biol. 2002;110:125-134. 7. Klein NP, Fireman B, Goddard K, et al. Vaccine effectiveness of cell-culture relative to egg-based inactivated influenza vaccine during the 2017-18 influenza season. PLoS ONE. 2020;15(2):e0229279. doi:10.1371/journal.pone.0229279 8. DeMarcus L, Shoubaki L, Federinko S. Comparing influenza vaccine effectiveness between cell-derived and egg-derived vaccines, 2017-2018 influenza season. Vaccine. 2019;37(30):4015-4021. doi:10.1016/j.vaccine.2019.06.004 9. Bruxvoort KJ, Luo Y, Ackerson B, et al. Comparison of vaccine effectiveness against influenza hospitalization of cell-based and egg-based influenza vaccines, 2017-2018. Vaccine. 2019;37(39):5807-5811. doi:10.1016/j.vaccine.2019.08.024 10. Boikos C, Sylvester GC, Sampalis JS, Mansi JA. Relative effectiveness of the cell-cultured quadrivalent influenza vaccine compared to standard, egg-derived quadrivalent influenza vaccines in preventing influenza-like illness in 2017-2018. Clin Infect Dis. 2020;ciaa371. doi:10.1093/cid/ciaa371 11. Divino V, Krishnarajah G, Pelton SI, et al. A real-world study evaluating the relative vaccine effectiveness of a cell-based quadrivalent influenza vaccine compared to egg-based quadrivalent influenza vaccine in the US during the 2017-18 influenza season. Vaccine. 2020;38(40):6334-6343. doi:10.1016/j.vaccine.2020.07.023 12. Izurieta HS, Chillarige Y, Kelman J, et al. Relative effectiveness of cell-cultured and egg-based influenza vaccines among elderly persons in the United States, 2017-2018. J Infect Dis. 2019;220(8):1255-1264. doi:10.1093/infdis/jiy716 13. Izurieta HS, Chillarige Y, Kelman J, et al. Relative effectiveness of influenza vaccines among the United States elderly, 2018-2019. J Infect Dis. 2020;222(2):278-287. doi:10.1093/infdis/jiaa080 14. Krishnarajah G, Divino V, Postma MJ, et al. Clinical and economic outcomes associated with cell-based quadrivalent influenza vaccine vs. standard-dose egg-based quadrivalent influenza vaccines during the 2018-19 influenza season in the United States. Vaccines (Basel). 2021;9(2):80. doi:10.3390/vaccines9020080 15. Boikos C, Fischer L, O'Brien D, Vasey J, Sylvester GC, Mansi JA. Relative effectiveness of the cell-derived inactivated quadrivalent influenza vaccine versus egg-derived inactivated quadrivalent influenza vaccines in preventing influenza-related medical encounters during the 2018-2019 influenza season in the United States. Clin Infect Dis. 2021;73(3):e692-e698. doi:10.1093/cid/ciaa1944 16. Izurieta HS, Lu M, Kelman J, et al. Comparative effectiveness of influenza vaccines among U.S. Medicare beneficiaries ages 65 years and older during the 2019-20 season. Clin Infect Dis. 2020;19;ciaa1727. doi:10.1093/cid/ciaa1727 17. Divino V, Anupindi VR, DeKoven M, et al. A real-world clinical and economic analysis of cell-derived quadrivalent influenza vaccine compared to standard egg-derived quadrivalent influenza vaccines during the 2019-2020 influenza season in the United States. Open Forum Infect Dis. 2021;9(1):ofab604. doi:10.1093/ofid/ofab604 18. Centers for Disease Control and Prevention. How flu vaccine effectiveness and efficacy are measured. Accessed September 23, 2022.. https://www.cdc.gov/flu/vaccines-work/effectivenessqa.htm 19. Katkade VB, Sanders KN, Zou KH. Real world data: an opportunity to supplement existing evidence for the use of long-established medicines in health care decision making. J Multidiscip Healthc. 2018;11:295-304. doi:10.2147/JMDH.S160029 22. Centers for Disease Control and Prevention. Key facts about seasonal flu vaccine. Accessed September 22, 2022. https://www.cdc.gov/flu/prevent/keyfacts.htm