Influenza
Olivia C. Welter, PharmD
During a March 2024 meeting, FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) made recommendations on which influenza viruses would be best to include in influenza vaccine compositions for the 2024–2025 flu season.
VRBPAC ultimately decided to recommend that manufacturers focus production efforts on trivalent vaccines going forward rather than continue making any quadrivalent vaccines, suggesting removal of a B-lineage component of the vaccine due to the virus strain’s lack of circulation.
B/Yamagata lineage virus no longer a threat
Each year, public health experts review U.S. flu vaccines to determine whether any composition changes need to be made based on a number of factors. One such factor is the active circulation of influenza virus strains identified through global surveillance.
Since the 2013–2014 flu season, patients have been able to receive quadrivalent flu vaccines, which are composed of influenza A(H1N1), A(H3N2), B/Victoria lineage, and B/Yamagata lineage components—all determined to be a threat to public health.
In the fall of 2023, VRBPAC evaluated data from across the world and found that B/Yamagata lineage viruses have had no confirmed circulation detections since March 2020. Because of this, VRBPAC voted unanimously to recommend the immediate removal of the B/Yamagata lineage component of influenza vaccines for the American public.
Trivalent vaccine formulations
VRBPAC recommends different vaccine compositions based on production method, meaning egg-based trivalent flu vaccines will have some different strains than cell- or recombinant-based trivalent flu vaccines for the 2024–2025 influenza season.
VRBPAC recommended egg-based vaccine formulations include the following components: an A/Victoria/4897/2022 (H1N1)pdm09–like virus, an A/Thailand/8/2022 (H3N2)–like virus, and a B/Austria/1359471/2021 (B/Victoria lineage)–like virus.
VRBPAC recommended cell- and recombinant-based vaccine formulations to include the following components: an A/Wisconsin/67/2022 (H1N1)pdm09–like virus, an A/Massachusetts/18/2022 (H3N2)–like virus, and a B/Austria/1359417/2021 (B/Victoria lineage)–like virus.
Quadrivalent vaccine utility
Although the United States will transition to only administering trivalent flu vaccines during the 2024–2025 season, many other countries may still plan to use quadrivalent vaccine formulations. Any manufacturer who has FDA approval for a quadrivalent flu vaccine will be able to export such vaccine doses to other countries if they choose to continue quadrivalent vaccine production.
VRBPAC has issued a recommendation for those manufacturers to include a B/Phuket/3073/2013 (B/Yamagata lineage)–like strain to any quadrivalent egg-, cell-, or recombinant-based vaccines that will be exported.
Information for pharmacy professionals
Many vaccine distributers are already accepting orders for the 2024–2025 flu season. Individuals who conduct ordering for their pharmacy can verify with their wholesalers and distributors whether they are able to begin preparations for the flu season by prebooking orders.
For the past several years, pharmacy technicians have been able to administer flu vaccines to patients due to provisions outlined in the PREP Act.
However, the PREP Act is set to expire at the end of 2024. Pharmacy professionals should plan to review the laws in their jurisdiction to determine whether pharmacy technicians at their pharmacy can administer flu vaccines in 2025.
Beginning with the 2023–2024 season, additional safety measures are no longer recommended for influenza vaccination in the presence of egg allergy. Some patients with egg allergies may still be wary of receiving an egg-based vaccine, so pharmacists should be prepared to counsel patients to increase their confidence in safely receiving the flu vaccine. Providing a sense of security by assuring patients that the pharmacy has medication prepared to treat an allergic reaction and having the patient stay in the pharmacy area for monitoring after receiving the vaccine can be helpful strategies. ■