The Influenza Vaccine is a preventive vaccine that helps protect against seasonal influenza (flu), a contagious viral infection that affects the nose, throat, and lungs. It reduces the risk of getting influenza and lowers the chances of severe illness, hospitalisation, and flu-related complications, particularly in children, older adults, pregnant women, and people with chronic medical conditions. It is administered by a healthcare professional and is updated periodically to match the influenza virus strains expected to circulate during each flu season.

Therapeutic Class: Preventive vaccine against seasonal influenza.

Pharmacological Class: Inactivated influenza vaccine (most commonly quadrivalent).

Drug Family: Influenza vaccines.

ATC Classification: J07BB02 (Influenza, inactivated, split or surface antigen).

Approved:

• Prevention of seasonal influenza caused by vaccine-covered influenza A and B virus strains.

• Reduction of flu-related complications in eligible individuals.

Commonly used for:

• Annual vaccination for children and adults.

• Protection of older adults, pregnant women, healthcare workers, and people with chronic illnesses.

Off-label use (only under medical guidance):

• No routine off-label therapeutic use. The vaccine prevents influenza and does not treat an active flu infection.

●       Injection (intramuscular, inactivated or recombinant vaccine): standard prefilled syringe, typically 0.5 mL per dose for adults, with age-specific dosing for young children.

●       Nasal spray (live attenuated vaccine): an alternative to injection, approved for a specific age range (typically 2 to 49 years, healthy and not pregnant) depending on the product and current guidance.

The Influenza Vaccine contains inactivated influenza virus components that cannot cause influenza. After vaccination, the immune system produces antibodies that recognise the influenza virus, helping prevent infection or reduce the severity of illness if exposure occurs later. Because influenza viruses change frequently, the vaccine formulation is updated periodically to match the strains expected to circulate during each flu season.

• Standard schedule (most people): One dose annually, ideally given before flu season begins, as the specific viral strains in the vaccine are updated each year based on global surveillance data.

• Condition-wise schedule: Young children receiving the vaccine for the first time may need two doses in their first season, spaced about 4 weeks apart, per current pediatric immunization guidance.

• Route: Intramuscular injection (most formulations) or intranasal spray (live attenuated formulation, where applicable).

• Missed/delayed dose: There is no fixed interval requirement between yearly doses beyond ensuring vaccination occurs before or during the relevant flu season; a delayed dose can simply be given when next available.

• Not applicable: Overdose is not a relevant concept for this vaccine in the way it is for a drug with dose-dependent toxicity.

Common:

• Pain, redness, or swelling at the injection site.

• Mild fever.

• Fatigue.

• Headache.

• Muscle aches.

Serious:

• Severe allergic reactions (rare).

• Fainting after vaccination.

• Rare reports of Guillain-Barré Syndrome (GBS).

Emergency symptoms: Seek immediate medical attention if you develop:

• Difficulty breathing.

• Swelling of the face or throat.

• Severe rash.

• Persistent dizziness or collapse.

Recovery advice: Most side effects are mild and settle within one to two days. Resting, staying hydrated, and moving the vaccinated arm gently may help reduce discomfort.

Pregnancy: Recommended during pregnancy because it helps protect both the mother and the baby from influenza-related complications.

Breastfeeding: Safe during breastfeeding.

Liver disease: No routine dose adjustment is required.

Kidney disease: Recommended for people with kidney disease because they are at higher risk of severe influenza.

Elderly: Strongly recommended for adults aged 65 years and older.

Children: Approved for eligible children from 6 months of age, with age-specific dosing recommendations.

Others: People with a history of severe allergic reactions to a previous influenza vaccine should consult their healthcare provider before vaccination.

• Immunosuppressive medicines may reduce the immune response to the vaccine.

• The Influenza Vaccine can generally be administered alongside other routine vaccines using different injection sites.

• Inform your healthcare provider about all medicines and vaccines you are receiving before vaccination.

• Observation for about 15 minutes after vaccination for allergic reactions or fainting.

• Annual vaccination before or during the influenza season for continued protection.

• Monitor for persistent or unusual symptoms following vaccination.

Not applicable in the traditional sense — annual influenza vaccination itself is the primary preventive strategy; antiviral medicines (e.g., oseltamivir) are used for treatment rather than prevention, and are not a substitute for vaccination.

The Influenza Vaccine is generally administered as a standalone preventive vaccine. It may be given during the same healthcare visit as other recommended vaccines, including COVID-19 vaccines, using separate injection sites when appropriate.

1. https://www.who.int/news-room/fact-sheets/detail/influenza-(seasonal )

2. https://www.who.int/publications/i/item/who-wer9729 

3. https://www.cdc.gov/flu/vaccines/index.html 

4. https://iapindia.org/immunization

The information on this page is for educational purposes only and is not a substitute for medical advice. Please consult your doctor to know if this treatment is appropriate for your condition.