The flu vaccine is safe and effective, but like any vaccine, some people might experience side effects. Knowing what to expect can help ease your worries.
Common flu vaccine side effects
Most side effects are mild and don’t last long. The usual side effects include:
- soreness, redness, or swelling where the vaccine was given
- low-grade fever
- muscle aches
- tiredness
- headache
These side effects usually show up within a few hours to a day and go away after a few days [3]. For most people, these symptoms are a sign that the body is building protection against the flu virus. These symptoms can be managed by resting, staying hydrated, and using over-the-counter pain relievers if needed. Nasal flu vaccines can have different side effects, like a runny or blocked nose, sore throat, or cough [2].
Children who receive the nasal spray may also experience mild symptoms such as wheezing, which typically resolves within a few days. Long-term side effects are very rare, and most side effects don’t last [1]. It’s worth noting that severe allergic reactions are extremely rare but can include hives or swelling. If any severe reactions occur, immediate medical attention should be sought.
How long side effects typically last
Most side effects go away in one to three days. Some people might feel tired or uncomfortable for up to a week [3]. If side effects last longer, it’s best to speak to a doctor. For example, a low-grade fever or muscle aches that persist beyond three days could indicate a different underlying issue. Side effects from the nasal flu vaccine, like a blocked nose or sore throat, might last for a few days [2]. While these side effects may be inconvenient, they are generally not a cause for concern. Drinking plenty of fluids and getting enough rest can help ease these symptoms. The duration of side effects can also vary based on factors such as age and overall health. Older adults or those with weakened immune systems might experience side effects that last a little longer [4].
Nasal vs. injection side effects
The type of flu vaccine you get can affect the side effects:
Injection (inactivated vaccine): Common and usually causes arm pain, fever, or muscle aches [4]. Arm pain occurs due to the body’s immune response as it starts to create antibodies. This pain can be managed by applying a cool compress to the site and avoiding heavy lifting for a day or two. Other mild side effects include fatigue and headache, which are signs of the body building protection.
Nasal (live vaccine): Usually given to children, a nasal vaccine may cause a runny nose, reduced appetite, or irritability [1]. The nasal vaccine uses a weakened form of the virus, which can sometimes result in mild cold-like symptoms. These symptoms are typically short-lived and manageable. Parents should note that children might also experience a slight decrease in appetite or increased tiredness for a day or two after the nasal vaccine. These effects are generally mild and should not be a cause for worry unless they persist for an extended period.
Both types are good at preventing flu but might be better for different people depending on health needs. For instance, people with a fear of needles might prefer the nasal spray, while others who have certain medical conditions might only be eligible for the injected form. The injected vaccine is inactivated, meaning it cannot cause the flu, which reassures many people who may be concerned about getting sick from the vaccine.
Conditions to disclose before getting vaccinated
Before getting the flu vaccine, tell your doctor if you have:
- severe allergies to any part of the vaccine
- a history of Guillain-Barré Syndrome
- a current illness with a high fever
- chronic conditions like asthma or heart disease [3]
This helps make sure the vaccine is safe for you. For example, people with egg allergies should let their doctor know, as some flu vaccines contain small amounts of egg protein. Your doctor might recommend an egg-free vaccine if needed. Those with a history of severe allergic reactions to any vaccine component should discuss the risks and benefits with their healthcare provider.
It’s also important to mention if you have any weakened immune conditions, as this may affect which type of flu vaccine is best for you. People on immunosuppressant medications or those undergoing treatments like chemotherapy should also inform their doctor so that they can receive tailored advice.
Flu vaccine and pregnancy/children
Pregnancy
The flu vaccine is safe for pregnant women and helps protect both mum and baby. The injected vaccine, which has an inactivated virus, is safe at any stage of pregnancy. Mild side effects, like soreness or a low fever, might happen but are usually not an issue [5]. The benefits of the flu vaccine during pregnancy go beyond just protecting the mother. It also helps protect the baby after birth during their first few months of life when they are most vulnerable. Pregnant women are more likely to have severe flu symptoms, so getting vaccinated can prevent complications such as preterm birth or severe respiratory problems. While side effects are generally mild, if a pregnant woman experiences any concerning symptoms after getting the vaccine, she should reach out to her healthcare provider.
Children
Children over six months can get the flu vaccine. Nasal spray is often preferred as it’s needle-free and easier to administer. Side effects might include a runny nose, reduced appetite, or slight irritability [1]. The flu can be particularly serious for young children, so vaccination is an important step in preventing illness. Side effects for children are generally mild and like those experienced by adults.
Parents should monitor their child for any reactions and ensure they stay hydrated and rested. If a child experiences wheezing or difficulty breathing, parents should contact a doctor. The nasal spray vaccine, while effective, is not suitable for children with certain medical conditions like severe asthma or weakened immune systems. In such cases, the injected vaccine might be recommended by a healthcare provider.
When to consult a healthcare provider
Most side effects from the flu vaccine are minor, but you should see a doctor if:
- you have a severe allergic reaction, such as hives or trouble breathing [3]
- a fever lasts more than 48 hours after the vaccine
- there is severe or long-lasting pain at the injection site
It’s also a good idea to consult a healthcare provider if you experience side effects that interfere with daily activities or if you develop symptoms not commonly associated with the vaccine, like severe headaches or persistent dizziness. These could indicate a different issue that needs attention. Monitoring your health and reaching out when something feels off can help catch and address any problems early. Immediate medical attention is needed for any severe reactions, such as swelling of the face or throat, as this could signal an allergic response that requires urgent care.
The flu vaccine is important for preventing flu and keeping people healthy. Side effects are usually mild and don’t last long. Letting your doctor know about any health conditions and knowing when to get help can make the process safer.
How HealthHero can support you
HealthHero offers support for those with questions about vaccinations by providing professional advice through GP consultations. To learn more, visit our GP consultation page.
