Autumn and winter are the peak season for influenza. Influenza is not the same as the common cold: it can trigger pneumonia, myocarditis and other serious complications, and older adults, infants and young children, people living with chronic disease and pregnant women are all at higher risk.
Vaccination is the most economical and most effective way to prevent influenza and its severe complications, and it is recommended every year.
For the 2026 influenza season, the trivalent inactivated split influenza vaccine manufactured by Sanofi Pasteur — sold under the brand name Vaxigrip — is suitable for people aged 6 months and older. This article sets out the vaccine’s strain composition, number of doses, contraindications and special-population considerations, based on the latest 2026 vaccine information.
The most economical and effective protection against influenza and its severe complications is an annual flu vaccine — timed well before the season peaks.
What kind of vaccine is it?
Sanofi Pasteur’s product is a trivalent inactivated split influenza vaccine. It protects against two influenza A viruses and one influenza B virus. It is produced using a split, inactivated process that contains no live virus, so vaccination itself cannot cause influenza infection.
The vaccine is suitable for people aged 6 months and older, including infants and young children, adults and older adults. Whether pregnant and breastfeeding women can use it should be decided by a doctor after weighing the benefits and risks.
Before vaccination, it is also worth noting the residual components. The vaccine contains residues of neomycin, formaldehyde and Triton X-100, and people allergic to any of these components should not be vaccinated. If you have a severe egg allergy, please tell the doctor your allergy history truthfully before vaccination, so that the doctor can assess whether it can be given.
Which strains are in the 2026 trivalent vaccine?
Influenza viruses mutate continually, and the strains circulating in each season may differ, so the World Health Organization updates its recommended vaccine composition every year.
The recommended composition of trivalent influenza vaccines for the 2026–2027 Northern Hemisphere season is:
- A/Missouri/11/2025 (H1N1)pdm09-like virus
- A/Darwin/1454/2025 (H3N2)-like virus
- B/Tokyo/EIS13-175/2025 (B/Victoria lineage)-like virus
This year’s Sanofi Pasteur influenza vaccine matches all three of the recommended strains, and all three components have been updated compared with the previous season. Only by vaccinating promptly with this season’s vaccine can you gain immune protection against the strains currently in circulation.
If you already received a flu vaccine in the first half of 2026, it is recommended that you wait until at least six months have passed since that dose before vaccinating again this season.
How it is given: dose, site and number of doses
The single dose of this season’s Sanofi trivalent vaccine is 0.5 mL, given by intramuscular injection.
For infants aged 6 to 12 months the anterolateral thigh is the preferred injection site; for people aged 13 months and older the deltoid muscle of the upper arm is preferred.
The number of doses is the part people most often get wrong. Infants and young children aged 6 to 35 months need two doses this season, regardless of whether they have had a flu vaccine in previous years, with the two doses at least 28 days (four weeks) apart. People aged 3 years and older need only one dose.
It usually takes two to three weeks after vaccination to develop antibodies at a protective level, so it is best to complete vaccination early, in September or October. Antibody protection lasts roughly five to seven months and gradually declines over time.
Who can be vaccinated, and who should not be
Do not vaccinate
People allergic to any component, excipient or residue of this vaccine — such as neomycin, formaldehyde or Triton X-100 — should not be vaccinated.
Postpone vaccination
People with moderate to severe fever, or in the acute phase of an infection, should wait until they have recovered before being vaccinated.
Use with caution — doctor assessment required:
- People with a severe egg allergy. The product may contain trace amounts of ovalbumin or chicken-derived protein, so it should not be given directly and must be used with caution after a doctor’s assessment.
- Pregnant and breastfeeding women. There is currently no domestic clinical trial data on this vaccine in pregnant or breastfeeding women, so an in-person consultation is advised before vaccination so that the doctor can assess the benefits and risks before a decision is made.
- People with immune deficiency or those taking immunosuppressant medication long term. You must tell the doctor before vaccination, because immunosuppressants may reduce the immune response to the vaccine.
- People with a history of severe allergy or of Henoch-Schönlein purpura. A doctor’s assessment is needed before vaccination; if Henoch-Schönlein purpura occurs after vaccination, seek medical attention promptly and remain alert to the complication of purpura nephritis.
What if other vaccines are also needed?
This vaccine can be given at the same time as other vaccines, but it should be injected into a different limb.
If you prefer to receive them separately, it is recommended to leave an interval of more than two weeks from other inactivated or live-attenuated vaccines; special circumstances can be handled at the doctor’s discretion. If another vaccine is given at the same injection site, the two vaccinations should be at least 14 days apart, and preferably more than 28 days apart.
What to watch for after vaccination
1. Stay for observation for at least 30 minutes. This is to guard against rare acute allergic reactions and to watch for psychogenic syncope — fainting from the sight of a needle, for example — so that a fainting episode does not lead to a fall injury.
2. Common reactions are usually mild. Pain, redness or swelling at the injection site, along with fever and muscle aches, mostly resolve on their own within one to three days after vaccination.
3. A small number of recipients may have false-positive results. If serological tests such as HIV or hepatitis C testing are carried out within a few days of vaccination, false-positive results are possible. If you have such tests scheduled soon, please tell the laboratory physician in advance.
4. Antibodies take time to develop. Antibodies are produced about two to three weeks after vaccination, so short-term exposure to an influenza environment can still lead to infection. Please keep up your protective measures.
A flu vaccine protects only against influenza virus — not against the common cold — and its value lies in lowering the risk of severe illness, not in eliminating infection entirely.
A word of caution
The influenza vaccine provides protection only against influenza viruses and cannot prevent the common cold. Its role is to reduce the risk of severe illness after infection and to reduce influenza-related complications, rather than to prevent infection 100 percent of the time.
If you have a contraindication, please do not force vaccination. Pregnant women, and people with severe allergy or immune deficiency, must be assessed by a doctor before vaccination. The vaccine package insert and the doctor’s in-person assessment remain the final reference.
About the author
Dr. Zhang Jing — Paediatrician, Beijing United Family Hospital
Doctor’s message: “To be a guardian on children’s path of growth, and to bring children healthy smiles.”
Areas of expertise:
- Diagnosis and treatment of common and frequently occurring neonatal diseases, and the rescue of critically ill newborns; skilled in specialist procedures including mechanical ventilation, lumbar puncture, endotracheal intubation, abdominal paracentesis and thoracic paracentesis.
- Diagnosis and treatment of common and frequently occurring paediatric diseases.
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