Influenza Vaccine Clinical Trials, Effectiveness, Side Effects 2024
Influenza vaccines, known as flu shots, protect people against influenza viruses each flu season, say the U.S. Centers for Disease Control and Prevention (CDC), the European Medicines Agency (EMA), and the World Health Organization (WHO). The WHO says that influenza vaccines do not cause seasonal flu since they are made with either killed or weakened viruses. Influenza vaccines are manufactured differently and have various indications and effectiveness.
Southern Hemisphere Influenza Vaccines 2025
The U.S. FDA's VRBPAC committee met on October 10, 2024, to discuss the strain selection for Influenza Virus Vaccines for the 2025 Southern Hemisphere flu season. On September 27, 2024, the WHO announced its recommendations for the viral composition of influenza vaccines for the 2025 influenza season in the Southern Hemisphere. On October 3, 2024, the CDC reported that five Southern Hemisphere countries reported flu shots were 35% effective during the last flu season.
U.S. FDA Influenza Vaccine Formulations 2024-2025
The U.S. Food and Drug Administration's (FDA) Vaccines and Related Biological Products Advisory Committee (VRBPAC) met on March 5, 2024. They finalized the quadrivalent and trivalent influenza vaccine options for the 2024-2025 flu season. The WHO recommended on February 23, 2024, that trivalent vaccines for use in the 2024-2025 northern hemisphere influenza season contain the following: Egg-based vaccines - an A/Victoria/4897/2022 (H1N1)pdm09-like virus; an A/Thailand/8/2022 (H3N2)-like virus; and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus. Cell culture- or recombinant-based vaccines: 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. For quadrivalent egg- or cell culture-based or recombinant vaccines for use in the 2024-2025 northern hemisphere influenza season, the WHO recommends the inclusion of the following as the B/Yamagata lineage component: a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
U.S. CDC Influenza Vaccine Recommendations 2024-2025
On August 29, 2024, the U.S. Centers for Disease Control and Prevention (CDC) published updates (73(5);1–25) on the 2023–24 recommendations of the Advisory Committee on Immunization Practices (ACIP) concerning the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2022;72[No. RR-2]:1–24). The ACIP meeting in June 2024 included presentations led by Lisa Grohskopf, Jill Ferdinands, and Lenee Blanton Influenza Division, CDC/NCIRD - Influenza Updates, Work Group Considerations, and Proposed Recommendations for the 2024-25 Influenza Season. The Influenza Work Group leader, Dr. Jamie Loehr, led the presentations. As of August 2024, the CDC says all flu vaccines for the 2024-2025 season will be trivalent, and most will be thimerosal-free or thimerosal-reduced vaccine (91%), and about 21% of flu vaccines will be egg-free.
Flu Shots Administered and Availability
The CDC's Weekly Influenza Vaccination Dashboard reported that, as of September 21, 2024, over 92 million flu shots had been distributed in the U.S., targeting the 2024-2025 flu season, and 9.6% of adults reported receipt of an influenza vaccine. The CDC reported on May 25, 2024, that about 48% of U.S. adults received a flu shot during 2023-2024. About 158 million flu vaccines were distributed during the 2023-2024 flu season, 173 million during 2022-2023, and 194 million during 2021-2022. As of May 4, 2024, an estimated 37.61 million doses were administered in retail pharmacies, and physicians' medical offices administered an estimated 25.56 million flu shots.
Influenza Vaccine Effectiveness
The CDC's ACIP reviewed influenza Vaccine Effectiveness (VE) interum data from the 2023-2024 flu season on October 23, 2024. The CDC published data regarding the vaccine effectiveness during the 2009-2023 flu seasons. Anthony C. Fries, Ph.D., with the U.S. DoD, presented 'Influenza Surveillance and Mid-Season VE at the U.S. FDA Vaccines and Related Biological Products Advisory Committee meeting on March 5, 2024. The DoD calculated the Beneficiary VE for the 2023-2024 Mid-Season Influenza Estimates, which ranged from 43% to 53%. A meta-analysis of flu vaccine VE studies conducted from 2017 through 2022 and published in the journal Vaccines on February 28, 2024, shows real-world effectiveness of seasonal influenza vaccination averaged 41.4%. The flu shot VE varied substantially by virus type and age group.
Influenza Vaccine Options 2024
Physicians, nurses, and pharmacists can offer patients up to nine influenza vaccines for the 2024-2025 flu season. On July 9, 2024, CSl Seqirus announced that it was shipping its differentiated portfolio of trivalent influenza vaccine formulations in the United States in compliance with the U.S. FDA directive to remove the B/Yamagata strain.
Afluria is an egg-based influenza vaccine approved for use in eligible people six months and older.
Fluad is an adjuvanted seasonal influenza vaccine for adults 65 and older.
Flucelvax is the first and only trivalent cell-based influenza vaccine indicated for use in people six months and older.
Fluarix is prepared from influenza viruses propagated in embryonated chicken eggs.
Flulaval is a quadrivalent, split-virion, inactivated influenza vaccine from a virus propagated in the allantoic cavity of embryonated hens' eggs.
Fluzone Quadrivalent and trivalent inactivated vaccine prevents influenza disease caused by influenza A subtype viruses and type B viruses.
FluMist is an Intranasal, live quadrivalent vaccine containing four vaccine virus strains.
Flublok uses eggs. Therefore, it is not subject to the mutations sometimes introduced into the vaccine during egg adaptation, which can cause traditional vaccines to be ineffective. In addition, Flublok contains three times the antigen of standard-dose inactivated influenza vaccines.
Fluzone High-Dose contains four times the antigen of standard-dose inactivated influenza vaccines.
Influenza Vaccine China
AdimFlu-S (QIS) is a quadrivalent split inactivated vaccine containing hemagglutinin from four influenza virus strains (A and B). The China National Medical Products Administration approved Clover Biopharmaceuticals, Ltd.'s AdimFlu-S in January 2022 for individuals three years older. As of September 2023, AdimFlu-S has been listed in 26 provinces and municipalities in China. The Biologic License Application submission to the Brazilian Health Regulatory Agency (ANVISA) was completed for AdimFlu-S on November 6, 2023. After approval, Clover will work with its local partner to commercialize the product in Brazil.
SINOVAC's influenza vaccines expanded international market accessibility in the first half of 2023 by gaining more overseas market approvals, such as Pakistan and Chile. On August 31, 2023, a study found that the trivalent influenza vaccine was moderately effective, highly immunogenic, and generally safe for healthy male military service members.
Influenza Vaccine United Kingdom
The UKHSA reported flu vaccine uptake rates for winter 2023 to 2024 compared with 2022 to 2023, averaging about 41% and 49%. In the United Kingdom, the NHS published a summary of flu vaccine recommendations for the 2023-2024 influenza season. The U.K.'s NHS says nasal spray vaccine offers the best protection for children and will be available for most persons in 2023.
Flu Shot Immune Imprinting
The concept of "immune imprinting" originated with investigating immune responses to infection by divergent strains of influenza viruses. Scientists found that people had more robust neutralizing antibody responses toward influenza strains that they had been exposed to during childhood. Mechanistically, when different strains of a pathogen infect the host cell, the immune system dedicates most of the response toward recalling the immune effectors used for the original exposure instead of generating reactions against the new strains, thus resulting in immune evasion.
Flu Shot Price
The U.S. CDC claimed that the Vaccines For Children program is federally funded and provides influenza vaccines and medicines to children at no cost. Internationally, UNICEF offers various price information. According to Fortune Business Insights, the Global Influenza Vaccine Market size is estimated to reach USD 13.58 Billion by 2029, exhibiting a CAGR of 8.8% between 2022 and 2029. And InstantRx™ is a digital gateway empowering people to find flu shot prices easily.
Influenza Vaccine Candidates
An updated listing of flu shot candidates is posted at this PVax link.
Influenza Season 2024
As of 2024, flu season trends are published by Precision Vaccinations.
