VACCINE TYPE

Three major types are available in the U.S.:

• Inactivated influenza vaccine, Trivalent (IIV3)
  • Available as a high-dose vaccination
• Recombinant influenza vaccine, Trivalent (RIV3)
• Live attenuated influenza vaccine, Tririvalent (LAIV3)

All 2024-25 Influenza season vaccines will be trivalent vaccines as influenza B/Yamagata lineage is no longer circulating.

INDICATIONS

FORMS

*Prices represent the specified cost per unit and the "Average Wholesale Price" (AWP).
^Dosage is indicated in mg unless otherwise noted.

PATHOGEN DIRECTED PROTECTION

• Influenza A and B
• 2024 - 2025 season: removal of the influenza B/Yamagata lineage strain. All vaccines are trivalent formulations.
  
  • U.S. egg-based influenza vaccines: A/Victoria/4897/2022(H1N1)pdm09-like virus, A/Thailand/8/2022 (H3N2)-like a virus, B/Austria/1359417/2021-like (Victoria lineage) virus
  • U.S. cell culture-based vaccine (ccIIV4) and recombinant (RIV4) influenza vaccines: A/Wisconsin/67/2022 (H1N1)pdm09-like virus, A/Massachusetts/18/2022 (H3N2)-like virus, B/Austria/1359417/2021 (Victoria lineage)-like virus.
• No preferential recommendation is made for one influenza vaccine over another (including children, 2024-2025 season).
• Approximately 10 - 14 days are required to acquire immunologic protection.
  
  • Seroconversion in 76% and 66% of adults ages 18-49 and 50-64, respectively.
  • Titers ≥ 1:40 was achieved in 100% and 94% of adults ages 18-49 and 50-64, respectively.

DOSE/ADMINISTRATION

ADVERSE DRUG REACTIONS

VACCINE/DRUG INTERACTIONS

• Immunosuppressive therapies (corticosteroids, alkylating drugs, antimetabolites, and radiation): Do not co-administer LAIV. This may theoretically increase the risk of disseminated infection.
• It can be co-administered with the pneumococcal vaccine and the COVID vaccinations (Comirnaty, Spikevax, Novavax). In infants and children < 24 months, IIV can be co-administered with nirsevimab (Beyfortus) if indicated.
• There have been reports of the influenza vaccine inhibiting the clearance of warfarin, theophylline, and phenytoin, although controlled studies have shown inconsistent results.
• The attenuated intranasal influenza vaccine should not be administered until 48 hours after cessation of antiviral compounds. Antiviral drugs should not be administered until 2 weeks after administering the live attenuated intranasal influenza vaccine.

CONTRAINDICATIONS

• Egg allergy is no longer a contraindication to receipt of the influenza vaccine. It is no longer recommended that persons with an egg allergy with symptoms other than urticaria (e.g., angioedema, anaphylaxis) be vaccinated in a monitored space. Egg allergy alone necessitates no additional safety measures for influenza vaccine beyond those recommended for any vaccine recipient, regardless of the severity of the previous reaction to egg.
• LAIV: a history of hypersensitivity to vaccine components, children and adolescents (5-17 years of age) receiving aspirin, individuals with a history of Guillain-Barré syndrome, and individuals with immune deficiency diseases.
  • Children aged 6 to 12 months may have a higher rate of wheezing and hospitalization with LAIV.

IMMUNE RESPONSE

• 6 months- 8 years: 86% had antibody response with 2 doses, but only 27% with 1 dose.
  • ACIP emphasizes the importance of administering 2 doses of vaccine to all children aged 6 months to 8 years if they have not been vaccinated previously with either live or attenuated influenza vaccine.
    
    • Doses should be separated by at least 4 weeks. Second doses given up to 4 days early are considered acceptable.
    • Per the AAP, doses do not need to be the same brand. If appropriate for age and health status, children may receive IIV and LAIV in the same season.
    • Children 8 years old who require 2 doses of vaccine should receive both doses even if the child turns 9 years old between doses 1 and 2.
• Adults >65 years: Fluzone High-Dose elicited significantly higher hemagglutination inhibition (HI) titers against all three influenza virus strains. Compared to the standard Fluzone vaccine, the clinical effectiveness of the high-dose Fluzone vaccine appears more efficacious; however, no preferential recommendation (yet) has been made for high-dose Fluzone over standard-dose IIV.

CLINICAL EFFICACY

• Vaccine efficacy depends on the match of epidemic and vaccine strains; it has been consistently well-matched over the last decade. Prevention efficacy:
  
  • Young adults or healthy elderly: ~70%.
  • Elderly in nursing homes: 30-40%, but reduces influenza mortality by 80%.
  • Vaccine efficacy may be decreased in the elderly and immunosuppression.
  • High-dose vaccine (age > 65 yrs): relative efficacy, 24.2% compared to SIV, suggesting enhanced protection with HD vaccine.
• In adults, intranasally administered live attenuated vaccine resulted in a 40.9% reduction in febrile upper respiratory tract illnesses during a season with a poor match of epidemic and vaccine influenza strains.

OTHER INFORMATION

• Estimated vaccination coverage remains < 50% among all patients for whom routine annual vaccination is recommended, including young children and adults with risk factors for influenza complications, healthcare personnel (HCP), and pregnant women.
• Influenza is a major infectious cause of death in the U.S. (3,000 to 80,000 annually); most are elderly, in nursing homes, or have chronic diseases.
• Providing the vaccine to healthy adults generally reduces URIs and employee absenteeism, but conflicting data on cost-effectiveness.
• Healthcare workers should be vaccinated to protect patients and other healthcare workers; if given FluMist x 7d post-administration, they must avoid high-risk patient contact.
• LAIV is shipped refrigerated and should be kept refrigerated (35-46°F).
• Children with asthma or reactive airway disease, persons with underlying medical conditions with a higher risk for influenza complications, children aged 6-23 months, and persons aged >49 years should not receive LAIV.
• Serious flu-related complications have been reported in obese patients and post-partum women.
• Flu vaccination in the era of COVID-19
  • Influenza vaccination for individuals > 6 months of age to reduce the prevalence of influenza may reduce symptoms that might be confused with COVID-19, and increased influenza vaccination may mitigate the severity of influenza illness, reduce hospitalizations, and reduce intensive care unit admissions.
  • For those who have acute illness with suspected or laboratory-confirmed COVID-19 disease, consider delaying influenza vaccination until the acute illness has resolved.
  • Guidance is available at https://www.cdc.gov/vaccines/pandemic-guidance/index.html

Basis for recommendation

1. Grohskopf LA, Ferdinands JM, Blanton LH, et al. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2024-25 Influenza Season. MMWR Recomm Rep. 2024;73(5):1-25.  [PMID:39197095]

   Comment: Annual recommendations from the Advisory Committee on Immunization Practices for the 2024-25 influenza season. Changes to the guidelines are minimal but significant. Due to lack of activity, the influenza B virus/Yamagata lineage has been removed from vaccine formulations. Only trivalent vaccines will be offered for this season. Additionally, solid organ transplant recipients are eligible to receive HD-IIV3 and aIIV3.
   

References

2. Committee on Infectious Diseases. Recommendations for prevention and control of influenza in children, 2024-2025: Policy statement. Pediatrics. 2024. [PMID: 39183669].

   Comment: Annual recommendations from the Committee of Infectious Diseases of the American Academy of Pediatrics for the 2024-2025 influenza season.
   
   
   
   Rating: Important