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Influvac

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Influvac

Influvac_EN

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Medically reviewed

Laura Arias

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Influvac

What is Influvac? Overview and Identity

Property Description
Active Ingredients Influenza Virus Surface Antigens
Form Suspension for Injection
Pharmacological Class Vaccine (Active Immunizing Agent)
General Purpose Prophylaxis of Influenza (Flu Prevention)
Origin Derived (Biological Product; Inactivated Subunit)

Influvac is an Inactivated Influenza Vaccine that acts as an Active Immunizing Agent, with the primary general purpose of providing prophylaxis of influenza (prevention of the flu). It is indicated for use in adults and children from 6 months of age, a broad target group clinically recognized for benefiting from annual immunization. This biological product falls within the Vaccine pharmacological class, distinguishing it from medications designed to treat an existing infection. This type of vaccine is designed to protect individuals against the diseases caused by the specific flu virus strains contained in the vaccine. This means the medicine's main function is to prepare your body's defenses ahead of time against seasonal outbreaks.

Structurally, Influvac is a Subunit Influenza Vaccine, a specific formulation known for containing only highly purified viral fragments. The active ingredients are the Influenza Virus Surface Antigens, specifically Haemagglutinin (HA) and Neuraminidase (NA). These antigens are derived from inactivated virus strains chosen annually to match the expected circulating viruses, based on recommendations from global organizations. Pharmacological studies confirm that the core mechanism involves the safe introduction of antigens to stimulate the immune system to produce protective antibodies. Influvac is typically prepared as a Combination Product, often available in a quadrivalent (four-strain) formulation, and delivered as a sterile Suspension for Injection. This approach ensures the defense system can rapidly neutralize the threat, reducing the risk of flu infection for the designated patient groups.

Regulatory References

  1. CDSCO: Product Insert for Influvac Tetra

What side effects are possible with Influvac?

Possible Side Effects and Safety Information

The safety profile for Influvac is defined by official regulatory documentation, which classifies possible adverse reactions by the likelihood of their occurrence and the body system affected. Most reactions are local and transient, though rare, serious events are also documented.

Frequency-Classified Adverse Reactions

The majority of documented reactions fall into the Very Common or Common categories and typically resolve spontaneously within one to three days. These include local injection site pain, swelling, and redness, as well as systemic effects such as headache, fatigue, and myalgia (muscle pain).

Reactions classified as Uncommon include fever. Certain serious or rare events, such as allergic reactions leading to shock, Guillain-Barré syndrome (GBS), and vasculitis, are documented as Not Known frequencies, reflecting their post-marketing reporting status.

Population-Specific Safety and Constraints

The official label includes specific safety considerations. The pediatric population may experience additional Very Common systemic effects, including gastrointestinal symptoms like vomiting and diarrhoea, along with irritability and drowsiness. Individuals with a history of coagulation disorders or thrombocytopenia require careful consideration during administration due to the risk of bleeding.

Influvac is strictly contraindicated in individuals with hypersensitivity to the active ingredients or to any trace residues from the manufacturing process, such as formaldehyde, gentamicin, or egg proteins.

Overdose and Emergency Response

Influvac Overdose and when to seek help

The official regulatory profile for Influvac, an inactivated influenza vaccine, describes the response to the administration of an excessive volume based on management of reactions rather than a toxicological crisis.

Documented Overdose Presentation

Overdose is not expected to cause a unique toxic syndrome. Regulatory documentation states that an overdose is expected to result primarily in an intensification of known adverse events. These manifestations may include exaggerated local injection site reactions (such as increased pain, swelling, or redness) and systemic effects (such as pyrexia or malaise). The severity is assessed based on the intensity and duration of these resulting adverse reactions. No specific differential management or severity notes for distinct patient populations are explicitly documented in the official overdose section.

Regulatory-Mandated Emergency Actions

The primary regulatory instruction is to seek immediate medical attention for the assessment and management of the event. The official labeling confirms that no specific antidote is known for this vaccine. Therefore, management is restricted to symptomatic and supportive treatment to address the manifested symptoms. Close observation of the patient is mandated, and hospital monitoring may be required if severe or prolonged adverse reactions result from the over-administration event. The overdose must be reported to a healthcare professional or emergency services.

Therapeutic Uses of Influvac

What Influvac Treats: Main Uses and Benefits

Influvac is commonly used to support prevention against seasonal influenza illness and the disruptive symptoms associated with it. Yearly flu vaccination is an important public health measure for reducing the risk from flu and its potentially serious complications and is recommended for nearly everyone. It is applied to support the body's defenses during the flu season, helping to avoid the development of severe illness.

The primary purpose is to help manage symptoms associated with acute or disruptive episodes, which includes symptoms related to physical discomfort like high fever, debilitating muscle aches, and profound fatigue. This product is considered relevant for use in conditions where symptoms may intensify temporarily and is commonly used across patient groups from adults and children from six months of age, individuals with chronic heart, lung, or metabolic disorders, and pregnant women. It helps address symptom clusters related to systemic imbalance and symptoms that interfere with daily functioning.

“This support is particularly relevant for easing the overall symptom load by preventing the most intense manifestations of the illness.”

The benefit plays a role in managing risk by helping to reduce the possibility of serious complications, such as severe respiratory problems that may require acute medical attention.

Quick Fact: Relief for Systemic Discomfort

Eligibility and Restrictions for Use

The eligibility for Influvac is defined by regulatory bodies based on age and specific medical conditions. Influvac is officially indicated for use in adults and children from 6 months of age and older.

Category Official Regulatory Status
Age Groups Allowed Adults and children from 6 months of age and older.
Absolute Contraindication Known hypersensitivity to the active substances or to any excipients/trace components (e.g., egg proteins, formaldehyde, gentamicin).
Use Not Established Infants less than 6 months of age. Safety and efficacy data are not available for this group.
Conditional Deferral Immunization must be deferred in the presence of a febrile illness or acute infection.
Pregnancy/Lactation Use is permitted in all stages of pregnancy and during breast-feeding.

The vaccine is particularly recommended for those at increased risk of influenza complications, such as individuals with chronic pulmonary, cardiovascular, or metabolic disorders. Patients undergoing immunosuppressant treatment should be aware that their immune response may be diminished.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Official regulatory documents define the interaction profile of Influvac primarily through effects on the immune response and physical administration constraints. The label does not document any interactions mediated by cytochrome P450 enzymes or drug transporters (pharmacokinetic interactions).

Pharmacodynamic and Administration Restrictions

Interacting Substance/Class Officially Documented Effect Regulatory Restriction
Immunosuppressant Treatments May result in a diminished immunological response to the vaccine. Use with caution combinations.
Other Vaccines May lead to an intensification of adverse reactions when co-administered. Immunisation must be carried out on separate limbs.
Other Medicinal Products N/A The vaccine must not be mixed with other medicinal products prior to injection (incompatibility).

Following vaccination, false positive results have been officially observed in serology tests using the ELISA method for the detection of antibodies against certain viruses, including HIV1, Hepatitis C, and HTLV1. This is a recognized laboratory testing interference. Additionally, a population-specific caution exists for children and teenagers receiving long-term acetylsalicylic acid containing medication due to the documented risk of Reye's syndrome following a natural influenza infection.

Mechanism of Action

Influvac is an inactivated subunit influenza vaccine containing purified surface antigens, specifically haemagglutinin (HA) and neuraminidase (NA), corresponding to the four target influenza virus strains.

Upon administration, these viral surface proteins are presented to the host immune system. The core molecular pathway involves the uptake and processing of the antigens by antigen-presenting cells (APCs). The APCs then migrate to lymphoid tissues, where they present the processed antigens to T-lymphocytes and B-lymphocytes, initiating the adaptive immune response.

Downstream, this cellular interaction cascade drives the clonal expansion and differentiation of B cells into plasma cells and memory B cells. Plasma cells are the primary effectors, synthesizing and secreting large quantities of humoral antibodies (primarily IgA and IgG) specific for the presented HA and NA surface glycoproteins.

The system-level physiological consequence is the circulation of these specific antibodies. The antibodies function as neutralizing agents by binding to the HA and NA targets. Anti-HA antibodies inhibit viral attachment to host respiratory epithelial cells, while anti-NA antibodies interfere with the enzymatic cleavage of sialic acid residues, which is necessary for the newly formed virions to detach from the host cell surface and spread. This results in the establishment of a pool of specific, circulating, high-affinity antibodies.

Dosage and Administration Information

Instruction Map: How to use Influvac — Official Administration Guidelines

This section describes the high-level principles for using Influvac (or Influvac Tetra) as defined by official administration guidelines.

Administration Scope

Element Official Guideline
Route of Administration Administered via Intramuscular (IM) injection or Deep Subcutaneous (SC) injection. The product must never be given intravascularly (IV).
Dosing Schedule The standard dose for adults and children 9 years of age and older is a single 0.5 mL dose.
Annual Timing Administration is generally performed once before the beginning of the influenza season, and the dose must be repeated every year.
Preparation Requirements The suspension must be shaken well and allowed to reach room temperature prior to administration.
Age-Group Rules Children less than 9 years of age who have not been vaccinated with a seasonal influenza vaccine require a second dose of 0.5 mL given after an interval of at least 4 weeks. Safety and efficacy are not established for infants less than 6 months of age.
Special Conditions If co-administered with other vaccines, the injections must be given into separate limbs. Administration should proceed with caution in individuals with bleeding disorders due to the injection method.

Resulting Procedural Structure

The required steps for administration are highly standardized. The sequence involves allowing the product to reach room temperature, shaking the suspension well, and then administering the 0.5 mL dose into the muscle or deeply under the skin. The procedure is only altered for young children who have not been vaccinated previously, where a mandatory second dose is required after at least four weeks to complete the initial schedule.

This protocol establishes the correct route and preparation steps to ensure the product is used consistently as defined by product labels, focusing on a single, annual dose for most patients.

Recent Clinical Evidence

Evidence for Prophylaxis of Seasonal Influenza Illness

The research base for this vaccine class was evaluated for outcomes related to preventing seasonal influenza infection and related illness. Studies included Randomized Controlled Trials (RCTs) and systematic reviews that were applied in studies examining short-term or episodic symptom patterns. These studies monitored immunologic markers, such as antibody levels, as outcomes related to systemic or functional imbalance in healthy populations.

Research describes patterns measured during the study period where being vaccinated was observed in some studies to correlate with a lower incidence of laboratory-confirmed influenza compared to individuals who were not vaccinated. Findings describe group patterns related to antibody levels reaching certain predefined thresholds after administration, which was observed in some studies. However, the research describes that findings related to the outcome may vary across studies, often depending on the specific viral strains circulating during the season the study was conducted.

Research on Preventing Severe Outcomes and Complications

Research has also explored outcomes related to more severe health events for this vaccine class. Large-scale observational studies were used in observational settings evaluating outcomes reflecting daily functioning and physiological strain, such as the incidence of influenza-related hospitalization and emergency department visits. These studies monitored acute changes associated with conditions involving periods of heightened symptoms.

Studies reported measurements where being vaccinated was observed in some studies to correlate with a lower incidence of severe outcomes, including hospitalization for flu-related illness. This evidence contributes to the broader evidence landscape by providing context on how these patterns evolved in the observed populations during periods of high symptom activity.

Evidence in Special Populations

The vaccine was evaluated in specific groups where the risk of complications from influenza is a point of focus. Research examined both children (ge 6 months) and older adults (ge 65 years). Studies also explored populations with certain underlying chronic heart or lung conditions.

The evidence for older adults reports that immunologic responses (antibody levels) may be lower or more variable compared to younger, healthy adults, and this pattern was observed in some studies. In children receiving the vaccine for the first time, research describes that receiving two doses was observed in some studies to be a pattern related to a more robust initial immunologic response. Overall, the research helps contextualize how outcomes related to physical discomfort and systemic imbalance are measured across these diverse groups.

Long-Term Studies and Durability of Effect

Studies were conducted during periods of increased symptom activity and typically monitored the response for a defined interval. Researchers examined how long the immune response persisted throughout the single influenza season. The data show patterns related to antibody levels that may begin to decline in the months following vaccination.

This pattern suggests that the level of measurable immune response may vary later in the season. Long-term effects are not fully established, and there is limited information for long-term outcomes and the full effect of waning immunity on observed health patterns later in the season. Research continues to explore these short-term changes and the duration of the observed patterns. The overall evidence contributes to the broader evidence landscape related to seasonal immunization.

Research Gaps and Uncertainties

Research highlights what is known, but also the areas where findings are still developing. The primary uncertainty in the evidence landscape relates to how results may differ from one flu season to the next. This is because the evidence quality varies across studies and the results apply only to the populations studied and depend on the antigenic match between the vaccine strains and the circulating virus.

For studies that examine severe, real-world endpoints like hospitalization, the data are heavily reliant on observational designs. This type of research carries an inherent risk of selection bias, and these subgroup findings are uncertain. Overall, comparative evidence is lacking for some outcomes, and data for certain groups remain insufficient, meaning research is ongoing to provide more context.

Key Studies & References

  1. Public Assessment Report Scientific discussion Influvac Tetra suspension for injection in pre-filled syringe 0.5 ml Influenza v

Frequently Asked Questions (FAQ)

Common questions about Influvac (FAQ)

Q: Does Influvac contain mercury or thimerosal?

According to official product information, the presence of thimerosal, a mercury derivative used as a preservative, depends on the presentation of the vaccine. Single-dose syringes typically contain trace amounts of mercury or none at all. Multi-dose vials, however, may contain thimerosal as a preservative.

Q: Why is Influvac needed every year?

Official documents and research evidence indicate that annual revaccination is required for two main reasons. Research evidence suggests that the level of measurable immune response may begin to decline in the months following administration. Additionally, the specific viral strains circulating globally change every year, necessitating an update to the vaccine formula to match.

Q: How long after getting Influvac should I expect to have protection?

Protection generally takes about two weeks to develop after receiving the vaccine. This timeframe allows the immune system to fully process the antigens and build the specific antibodies needed for defense.

Q: Can I still get the flu even after receiving Influvac?

Official regulatory documents state that the vaccine may not elicit a protective immune response in all recipients. Furthermore, the vaccine is only intended to be effective against the specific strains used in the formula. Based on the documented limitations, receiving the vaccine does not guarantee complete protection against all forms of the influenza virus.

Q: Are there any long-term side effects associated with Influvac?

Research evidence indicates that long-term effects are not fully established due to the focus on seasonal studies. Rare and serious neurological events, such as Guillain-Barré syndrome (GBS), have been reported in the post-marketing surveillance system. These events are classified as having a 'Not Known' frequency because their occurrence rate cannot be reliably estimated from the available data.

Q: Can Influvac cause the flu?

No, the official mechanism of action indicates that Influvac is an inactivated subunit vaccine. This means it contains only purified fragments of the virus and is therefore unable to cause influenza illness.

Q: Is Influvac considered safe for people with egg allergies?

According to the official product information, Influvac is contraindicated (should not be used) in individuals with a known hypersensitivity to the active ingredients or to any trace components from manufacturing, including egg proteins. Regulatory labels state that the product contains no more than a trace amount of ovalbumin (egg protein) per dose.

Q: Does Influvac protect against all strains of the flu?

The vaccine is intended to provide protection against only the specific influenza virus strains from which it is prepared, along with closely related strains. Official information indicates that it is not effective against all possible strains of the influenza virus that may be circulating.

Q: Who is Influvac typically recommended for by health bodies?

Influvac is officially indicated for use in adults and children from 6 months of age. Health bodies typically aim this vaccine at individuals at increased risk of influenza complications, such as those with chronic heart, lung, or metabolic disorders.

Q: Is it true that different versions of Influvac are available in different years?

Yes, the official product composition is updated annually. This annual change is based on global surveillance recommendations to ensure the vaccine formula is matched to the specific influenza virus strains expected to circulate during the upcoming season.

Q: Does having a history of fever after previous flu shots mean I can't get Influvac?

According to the regulatory label, immunization should be deferred only in the presence of a current febrile illness (fever) or acute infection. A history of fever after receiving a previous flu shot is not typically listed as a contraindication in the official product information.

Q: What is the process for updating the Influvac vaccine formula each year?

The specific viral strains included in the vaccine are selected annually through a process coordinated by global organizations, such as the World Health Organization (WHO). The WHO monitors influenza viruses circulating worldwide and recommends strains for inclusion in vaccines manufactured for the upcoming season.

Q: Are there specific food or drug interactions listed for Influvac?

The regulatory label includes documented interactions with immunosuppressive treatments and co-administered vaccines. Specific food interactions are not documented in the official regulatory label.

Q: Does my blood type or general health status affect the effectiveness of Influvac?

Official information indicates that general health status may affect the immune response. For example, patients with conditions causing immunosuppression may have an insufficient antibody response. Antibody responses in older adults may also be lower or more variable. Blood type, however, is not listed as a factor.

Q: Is Influvac approved in countries outside of the United States?

Influvac is authorized and prepared in accordance with the World Health Organization (WHO) and national competent authority decisions for many regions globally. These regions include Europe, Canada, and Australia, among others.

Q: What does 'inactivated' mean when describing the Influvac vaccine?

'Inactivated' means the vaccine is manufactured using virus particles that have been chemically or physically killed (inactivated). This process ensures the vaccine does not contain any whole, live virus and therefore cannot cause influenza infection.

Q: What is the typical timeframe for minor side effects to appear and resolve?

Most local and general adverse reactions are mild to moderate in intensity and usually occur within the first 3 days following vaccination. These reactions typically resolve spontaneously within 1 to 3 days after their onset.

Q: How is the general safety of Influvac monitored after it is released each year?

The continued safety of the vaccine is monitored through a system of post-marketing surveillance. This regulatory process ensures that rare adverse events that occur after the vaccine is released to the public can be documented and classified.

How should Influvac be stored and disposed of?

How to Store and Dispose of Influvac

Influvac must be stored strictly according to official regulatory requirements to maintain its stability. The product requires cold chain storage in a refrigerator at a temperature between 2 C to 8 C.

Storage Rules

  • Do not freeze the vaccine, as freezing destroys the product.
  • Store in the original package to protect from light.
  • Keep the product out of the sight and reach of children.
  • Do not use the vaccine past the labeled expiry date.

Disposal Instructions

Unused or expired Influvac must be handled according to specific environmental guidelines. The product should not be disposed of via wastewater or household waste. Individuals must ask their pharmacist how to dispose of medicines no longer required or follow local waste disposal regulations.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

Equivalent of Influvac found in:

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