What Is the Flu Vaccine? When Should You Get It?
Learn when to get a flu vaccine, who benefits most, its use in children and pregnancy, how protection develops, and possible side effects.
The flu vaccine stimulates an immune response against influenza viruses, reducing the risk of catching flu and developing severe illness. It is reviewed each season and is usually given in autumn, before flu cases increase. It takes about two weeks for a protective response to develop. Missing vaccination in autumn does not necessarily mean it is too late for that season.
What Does the Flu Vaccine Do?
The vaccine helps the immune system recognise influenza viruses. Its purpose is not only to reduce the likelihood of getting flu; reducing the risk of severe illness and hospitalisation is also important. This benefit is particularly relevant to older adults and people with chronic conditions.
The flu vaccine does not protect against every respiratory infection. Viruses that cause the common cold, COVID-19 and other infections are different from influenza. A runny nose, cough or sore throat after vaccination does not, on its own, show that the vaccine has not worked. You can read about distinguishing flu from similar symptoms in our article on influenza symptoms and assessment.
When Should You Get the Flu Vaccine?
In Türkiye, flu vaccination is generally preferred in the autumn months. The aim is to allow a protective immune response to develop before influenza viruses become widespread in the community. Adult immunisation recommendations for Türkiye highlight October and November. However, there is no single date or fixed deadline that applies to everyone; age, health status, previous vaccinations and influenza circulation that year are considered together.
Vaccination can also be given in November, December or later. If influenza viruses are still circulating and an appropriate, unexpired vaccine for that season is available, vaccination may still be beneficial. People in higher-risk groups, in particular, should not wait until the following year simply because they missed autumn vaccination.
Protection does not begin on the day of vaccination. Because the immune response takes about two weeks to develop, someone exposed to the virus just before or shortly after vaccination can still get flu. The vaccine is not used to treat an influenza infection that has already started.
Who Is Vaccination Especially Important For?
The flu vaccine can be given from six months of age, using an age-appropriate product. Vaccination is especially important for people who are more likely to develop severe flu:
- People aged 65 years and over.
- Pregnant women.
- Children aged six months to under five years.
- People with chronic lung conditions such as asthma or COPD, heart disease, diabetes, chronic kidney disease, or a condition or treatment that suppresses the immune system.
- People living in nursing homes and long-term care settings.
Vaccination is also important for healthcare workers and people who care for individuals in higher-risk groups. People outside these groups can also discuss their vaccination needs with their doctor. The vaccine used must be appropriate for the person's age and health status.
How Many Flu Vaccine Doses Do Children Need?
Babies younger than six months are not given the flu vaccine. During this period, it is important to review the vaccination status of their caregivers and reduce contact with people who are ill.
Some children aged six months to eight years need two doses in the same season, depending on how many flu vaccine doses they have previously received. When two doses are needed, they are given at least four weeks apart. A paediatrician determines the plan for children whose vaccination history is unknown or who have not previously received enough flu vaccine doses. Bringing the child's vaccination records to the assessment is therefore helpful.
Can You Get the Flu Vaccine During Pregnancy or While Breastfeeding?
Pregnancy can increase the risk of severe flu. The inactivated flu vaccine, which does not contain live virus, can be given at any stage of pregnancy. In addition to protecting the mother, vaccination during pregnancy can help protect the baby during the first months after birth. The live attenuated nasal spray vaccine is not used during pregnancy.
Breastfeeding is not a contraindication to the inactivated flu vaccine. During pregnancy or breastfeeding, vaccine selection and timing should be assessed in light of vaccination records for the current season and the person's health status.
Why Is Vaccination Repeated Every Year?
Influenza viruses change over time, and immunity from a previous vaccination decreases. Vaccine composition is therefore reviewed each season; being vaccinated last year does not replace this year's vaccination.
The level of protection is not the same for everyone. Age, immune system function and the similarity between the viruses in the vaccine and those circulating that season affect the outcome. A vaccinated person may still get flu; vaccination helps reduce its more severe consequences. It would not be accurate to give a single protection percentage or a precise duration of protection that applies to everyone.
What Are the Possible Side Effects of the Flu Vaccine?
Pain, tenderness, redness or mild swelling may occur at the injection site. Some people develop short-lived tiredness, headache, muscle aches or a mild fever. These symptoms are usually mild and settle within a few days.
The inactivated flu vaccine does not cause influenza. Short-lived general symptoms after vaccination should be distinguished from an infection caused by another virus or from influenza itself. Symptoms that worsen or do not improve within the expected time should be reported to a healthcare professional.
If you develop difficulty breathing, swelling of the tongue or lips, or widespread hives together with dizziness or fainting after vaccination, go to an emergency department immediately. These may be signs of a rare, serious allergic reaction and must not be left untreated.
What Should You Tell the Healthcare Professional Before Vaccination?
If you have previously had a serious allergic reaction after a flu vaccine, or have a known severe allergy to one of its components, tell the healthcare professional before vaccination. A doctor should assess whether the same product can be used again and whether an alternative is suitable.
Egg allergy is not the same as a serious allergic reaction to a flu vaccine. Current guidelines do not consider egg allergy alone a reason to rule out all flu vaccines. However, your allergy history, current product information for the vaccine to be used in Türkiye and your individual health status should be assessed together.
Tell your doctor if you developed Guillain-Barré syndrome, a condition affecting the nerves that can cause weakness, within six weeks of a previous flu vaccination. In this situation, the benefits and risks of vaccination need individual consideration. Vaccination may need to be postponed if you have a moderate or severe acute illness.
Immunosuppressive medicines, cancer treatment or a history of organ transplantation can also affect vaccine choice and timing. Do not stop your regular medicines on your own in order to be vaccinated.
How Can You Continue Protecting Yourself After Vaccination?
Being vaccinated does not mean that everyday preventive measures can be abandoned. Cleaning your hands regularly, covering your mouth and nose when coughing, staying at home when you feel ill and reducing close contact help protect against respiratory infections.
If you are in a higher-risk group and develop fever, cough or marked tiredness that may suggest flu, seek medical advice early, even if you have been vaccinated. Shortness of breath, chest pain or changes in consciousness require urgent assessment. Do not delay seeking help for these symptoms on the assumption that vaccination provides complete protection.
This content provides general information; an individual vaccination plan requires assessment by a doctor.
Frequently Asked Questions
Yes. Having an infection with one influenza virus does not provide complete protection against the other influenza viruses circulating in the same season. It is also not always known whether the illness was actually influenza. Once the acute illness has resolved, the need for vaccination can be assessed with a doctor.
A mild upper respiratory tract infection alone is generally not a reason to postpone vaccination. With a moderate or severe illness, with or without fever, vaccination may need to be delayed. Tell the healthcare professional giving the vaccine about any symptoms you have that day.
The inactivated flu vaccine can be given on the same day as other appropriate vaccines, at different injection sites. A healthcare professional will assess the products to be used together with the person's vaccination schedule.
An additional flu vaccination is not routinely recommended for someone who has completed vaccination for that season. The initial schedule for children who need two doses because of their previous vaccination history is an exception. The date of the previous dose and the season it was intended for should be checked.
No. A protective immune response does not develop immediately, so vaccination does not provide instant protection after an exposure has already occurred. If you are in a higher-risk group or symptoms have started, do not delay assessment; the decision about vaccination and assessment of the current illness are considered separately.
