Based on the information provided, I can provide details about the influenza vaccine strains recommended for the 2025-2026 season. However, please note that the specific strains for 2026 have not been officially announced yet, as the recommendations are typically made a few months before the season starts. Here's what we know so far:
2024-2025 Season (as a reference):
For the 2024-2025 season, the U.S.-licensed egg-based influenza vaccines will contain the following strains:
- Influenza A/Victoria/4897/2022 (H1N1) pdm09-like virus
- Influenza A/Thailand/8/2022 (H3N2)-like virus
- Influenza B/Austria/1359417/2021 (B/Victoria lineage)-like virus (Source: CDC 2023-2024 summary of recommendations for influenza vaccine)
2025-2026 Season (projected based on current trends):
The World Health Organization (WHO) typically recommends strains for the forthcoming season based on the Global Influenza Surveillance and Response System. While the exact strains for 2025-2026 have not been confirmed, we can expect that the recommended strains will be updated to match the circulating viruses that are likely to be prevalent during that season.
Key points to consider:
- H3N2 Strain: The H3N2 strain is one of the most common causes of seasonal flu and undergoes frequent antigenic drift, requiring regular updates to the vaccine.
- H1N1 Strain: The H1N1 strain, similar to the 2009 pandemic strain, also requires frequent updates.
- Influenza B: The vaccine will likely include strains from both the Victoria and Yamagata lineages, although as noted, B/Yamagata viruses have not circulated significantly since March 2020 (Source: CDC).
Anticipated Updates:
Given that the influenza virus evolves continuously, the 2025-2026 vaccine will likely include updated strains of H1N1, H3N2, and one or two Influenza B strains to provide optimal protection. The specific strains will be determined by WHO's recommendations, which are usually announced in February or March before the Northern Hemisphere's flu season.
Additional Information:
- Adjuvanted Vaccines: For higher-risk populations, adjuvanted vaccines like Audenz (approved for H5N1) may be recommended. Ongoing studies for vaccines against other avian influenza subtypes, such as H7N9, may also lead to new vaccine options by 2026.
- Quadrivalent Vaccines: The shift to quadrivalent vaccines, which include two Influenza B strains, has been a standard practice since 2013. It's likely that this format will continue for the 2025-2026 season.
For the most accurate and up-to-date information, it is best to refer to the WHO's official recommendations when they are released, typically in early 2025 for the 2025-2026 season.