In short
This article examines several clinical trials investigating the use of the Influenza A/Victoria/4897/2022 IVR-238 (H1N1), Inactivated vaccine. These studies aim to assess the safety, efficacy, and immune responses generated by this influenza vaccine in various populations and contexts. The trials cover topics such as vaccine combinations, timing of administration, and effects on specific patient groups like those with coronary artery disease.
At a glance
- Vaccine Types
- Influenza A/Victoria/4897/2022 IVR-238 (H1N1), Inactivated; often part of quadrivalent influenza vaccines
- Study Populations
- Healthy adults (18-85 years), older adults (65+ years), patients with stable coronary artery disease
- Primary Outcomes
- Antibody responses, safety profile, reactogenicity
- Secondary Outcomes
- T cell responses, long-term immunity, effects on inflammatory markers
- Study Designs
- Randomized controlled trials, some with delayed-start or co-administration designs
- Special Focus Areas
- Co-administration with COVID-19 vaccines, timing of vaccination, effects in cardiovascular patients
- Follow-up Periods
- Ranging from 28 days to 6 months post-vaccination
- Safety Monitoring
- Adverse events, serious adverse events, local and systemic reactions
What is this influenza vaccine?
The influenza A/Victoria/4897/2022 IVR-238 (H1N1) inactivated vaccine is a component of several quadrivalent (four-strain) influenza vaccines developed for the 2023-2024 flu season. It contains an inactivated form of the influenza A H1N1 virus strain that was predicted to circulate. This particular strain is named after Victoria, Australia where it was first isolated in 2022.
This vaccine is included in products like VaxigripTetra, Influvac Tetra, and Fluad Tetra, which are designed to protect against four different influenza virus strains. The other strains typically include another influenza A subtype (H3N2) and two influenza B virus lineages.
How does it work?
As an inactivated vaccine, it contains killed influenza virus particles. When injected, these particles stimulate the immune system to produce antibodies against that specific strain of flu virus. If the vaccinated person later encounters the live virus, their immune system is primed to recognize and fight it off more effectively, reducing the risk of infection or severity of illness.
The inactivation process ensures the vaccine cannot cause influenza, as the virus particles are no longer capable of replication or causing disease.
Who is this vaccine for?
This influenza vaccine is generally recommended for individuals aged 6 months and older, with a particular focus on: Adults aged 65 years and older People with certain chronic medical conditions Pregnant women Healthcare workers Caregivers of high-risk individuals
Some formulations, like Fluad Tetra, are specifically designed for older adults (65+) and contain an adjuvant to boost immune response.
How effective is it?
The effectiveness of influenza vaccines can vary from year to year, depending on how well the selected strains match the circulating viruses. Generally, when there is a good match, flu vaccines can reduce the risk of illness by 40-60%.
Ongoing studies are evaluating the specific effectiveness of vaccines containing the A/Victoria/4897/2022 IVR-238 (H1N1) strain for the 2023-2024 season. Early results from clinical trials show promising immune responses, but real-world effectiveness data will be collected throughout the flu season.
How is it administered?
The vaccine is typically given as a single dose via intramuscular injection, usually in the upper arm (deltoid muscle) for adults and older children, or the thigh for infants. Some specific administration details include:
- Dosage: 0.5 ml for most formulations
- Timing: Ideally given before the start of flu season (usually September-November in the Northern Hemisphere)
- Frequency: Annual vaccination is recommended due to evolving flu strains and waning immunity
What are the potential side effects?
Most side effects of influenza vaccines containing the A/Victoria/4897/2022 IVR-238 (H1N1) strain are mild and short-lived. Common side effects may include:
- Pain, redness, or swelling at the injection site
- Headache
- Fatigue
- Muscle aches
- Low-grade fever
Serious allergic reactions are rare but can occur. Patients should seek immediate medical attention if they experience symptoms of a severe allergic reaction, such as difficulty breathing, rapid heartbeat, or dizziness.
Ongoing research
Several clinical trials are currently underway to further evaluate vaccines containing the A/Victoria/4897/2022 IVR-238 (H1N1) strain:
- A study is examining the effect of influenza vaccination timing on immune responses in adults aged 65 and over.
- Another trial is investigating the impact of influenza vaccination on inflammatory markers in patients with stable coronary artery disease.
- Researchers are also studying the co-administration of COVID-19 and influenza vaccines in older adults.
These ongoing studies aim to optimize vaccination strategies and understand the broader health impacts of influenza immunization, particularly in vulnerable populations.