April 23, 2024

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WHO: Latest 2024-2025 Influenza Vaccine Strain Recommendations

WHO: Latest 2024-2025 Influenza Vaccine Strain Recommendations



WHO: Latest 2024-2025 Influenza Vaccine Strain Recommendations

The influenza virus can cause seasonal flu and even pandemics. It is an RNA virus with a complex classification and many subtypes, making it prone to mutations.

Vaccination is widely recognized as the best way to prevent the flu.

To ensure vaccine effectiveness, the World Health Organization (WHO) updates the vaccine strain components annually.

Changes in the 2024-2025 Northern Hemisphere Influenza Vaccine Strain Composition

To maintain vaccine effectiveness, it is necessary to regularly update the influenza virus vaccine components.

After analyzing global influenza virus epidemiology, pathogenesis, and vaccine serology, WHO announced the 2024-2025 Northern Hemisphere Influenza Vaccine Strain Recommendations on February 23, 2024.

Trivalent Chicken Embryo Cultured Vaccines:

  • an A/Victoria/4897/2022 (H1N1)pdm09-like virus
  • an A/Thailand/8/2022 (H3N2)-like virus
  • a B/Austria/1359417/2021 (B/Victoria lineage)-like virus

Trivalent Cell-Cultured or Recombinant Protein Vaccines:

  • an A/Wisconsin/67/2022 (H1N1)pdm09-like virus
  • an A/Massachusetts/18/2022 (H3N2)-like virus
  • a B/Austria/1359417/2021 (B/Victoria lineage)-like virus

Quadrivalent Chicken Embryo and Cell-Cultured or Recombinant Protein Vaccines (added to the trivalent vaccine components):

  • a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus Since March 2020, no naturally occurring B/Yamagata lineage virus has been confirmed. WHO considers it unnecessary to include the B/Yamagata lineage virus as a component of influenza vaccines and recommends its removal from influenza vaccine components. In areas still using quadrivalent vaccines, the inclusion of the B/Yamagata lineage component remains consistent with previous recommendations.

Comparison of 2023-2024 and 2024-2025 Northern Hemisphere Influenza Vaccine Strain Components reveals the main difference in the H3N2 virus strains:

Vaccine type

2023-2024

2024-2025

Trivalent chicken embryo culture vaccine

A/Darwin/9/2021 (H3N2)-like virus

A/Thailand/8/2022 (H3N2) -like virus

Trivalent cell culture or recombinant protein vaccine 

A/Darwin/9/2021 (H3N2)-like virus

A/Massachusetts/18/2022 (H3N2)-like virus


Recombinant Antigens are Key Materials for Vaccine Research

Critical target antigens play an important role in influenza virus-related vaccines, drugs, and even diagnostic reagents. Below, we have organized information on HA, NA, and NP proteins.

protein

Function

application

HA

(Hemagglutinin)

Binds to sialic acid receptors on the host cell membrane to assist the fusion of the viral envelope and the host cell membrane; coagulation

Basic research on influenza

Flu vaccine development

Anti-hemagglutinin antibody development

Research on virus detection reagents

NA

(Neuraminidase)

Hydrolyzes sialic acid receptors to promote release of mature virus particles

Antiviral drug development

Basic research on influenza

Flu vaccine development

Antibody R&D

Research on virus detection reagents

NP

(nucleoprotein)

Combines with influenza genetic material to participate in viral gene replication, transcription, and translation; maintains viral gene stability

Antiviral drug development

Basic research on influenza

Antibody R&D

Diagnostic product development

Recombinant antigens from influenza vaccine strains can be applied in various stages of vaccine development, such as vaccine content testing, vaccine biological potency testing, and toxicity testing. Using recombinant antigens for ELISA testing can analyze the levels of total antibodies and neutralizing antibodies in immune sera after vaccination, and detect vaccine content using recombinant proteins as controls.

WHO: Latest 2024-2025 Influenza Vaccine Strain Recommendations

Using recombinant influenza HA protein to detect serum antibody levels in mice after vaccine immunization (picture from Andersen, et al.)

WHO: Latest 2024-2025 Influenza Vaccine Strain Recommendations

References:

[1]https://www.who.int/publications/m/item/recommended-composition-of-influenza-virus-vaccines-for-use-in-the-2024-2025-northern-hemisphere-influenza-season

[2] Andersen, et al. Pandemic Preparedness Against Influenza: DNA Vaccine for Rapid Relief.[J]. Frontiers in Immunology.2021.747032.

[3] Bangaru S , et al. A Site of Vulnerability on the Influenza Virus Hemagglutinin Head Domain Trimer Interface[J]. Cell, 2019.

[4] Kim M , et al. Inhibition of influenza virus internalization by (-)-epigallocatechin-3-gallate.[J]. Antiviral Research, 2013, 100(2):460-472.

(source:internet, reference only)


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