The flu is a respiratory infection that’s caused by the influenza virus. It can be spread from person to person through respiratory droplets or by coming into contact with a contaminated surface.

In some people, flu causes a mild illness. However, in other groups it can be potentially serious and even life threatening.

The seasonal flu shot is available every year to help defend against becoming sick with the flu. It protects against three or four strains of influenza that research has determined will be prevalent during the upcoming flu season.

The Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months and older get a flu shot each year. But what happens if you’re already sick? Can you still get a flu shot?

It’s safe to receive the flu shot if you’re sick with a mild illness. Some examples of a mild illness include colds, sinus infections, and mild diarrhea.

A good rule of thumb is to speak to your doctor prior to receiving the flu shot if you’re currently sick with a fever or have a moderate to severe illness. They may decide to delay your flu shot until after you’ve recovered.

What about the nasal spray vaccine?

In addition to the flu shot, a nasal spray vaccine is available for non-pregnant individuals who are between the ages of 2 and 49. This vaccine uses a weakened form of influenza that can’t cause disease.

As with the flu shot, people who have a mild illness can receive the nasal spray vaccine. However, people with moderate to severe illnesses may need to wait until they’ve recovered.

It’s important that children receive their vaccinations on time in order to be protected from potentially serious infections, including influenza. Children 6 months and older can receive the flu shot.

It’s safe for children to receive the flu shot if they have a mild illness. According to the CDC, children can still be vaccinated if they have:

If your child is currently sick and you’re unsure if they should receive a flu shot, discuss their symptoms with a doctor. They’ll be able to determine if your child’s flu shot should be delayed.

You may worry that getting vaccinated while sick could lead to lower protection levels since your immune system is already busy fighting an existing infection. However, a mild illness shouldn’t affect the way your body reacts to the vaccine.

Studies on vaccine effectiveness in people who are sick are rather limited. Some studies of other vaccines have indicated that having a mild illness at the time of vaccination doesn’t appear to affect the body’s response.

One risk of vaccinating while you’re sick is that it’ll be hard to distinguish your illness from a reaction to the vaccine. For example, is the fever that you have due to your preexisting illness or to a vaccine reaction?

Lastly, having a stuffy nose can impact the effectiveness of the delivery of the nasal spray vaccine. Because of this, you may choose to receive the flu shot instead or to delay vaccination until your nasal symptoms have cleared.

The flu shot can’t give you the flu. This is because it doesn’t contain a live virus. However, there are some potential side effects that you may experience following vaccination. These symptoms are usually short lived and can include:

Nasal spray side effects

The nasal spray may have some additional side effects. In children, these include things like runny nose, wheezing, and vomiting. Adults may experience a runny nose, cough, or sore throat.

Serious side effects

Serious side effects from flu vaccination are very rare. However, it is possible to have a severe allergic reaction to the vaccine. This typically happens within minutes to hours of getting vaccinated and can include symptoms like:

Weakness could indicate Guillain-Barré syndrome, a rare but serious autoimmune disorder. In rare instances, some people experience this condition after receiving the flu shot. Other symptoms include numbness and tingling.

If you think that you’re experiencing symptoms of Guillain-Barré syndrome or having a severe reaction to the flu vaccine, seek immediate medical attention.

The following people shouldn’t get the flu shot:

  • children who are younger than 6 months old
  • people who’ve had a severe or life threatening reaction to the flu vaccine or any of its components

You should also speak to your doctor before vaccination if you have:

  • a severe allergy to eggs
  • a severe allergy to any of the components of the vaccine
  • had Guillain-Barré syndrome

It’s also important to note that there are different formulations of the flu shot for people of different ages. Talk to your doctor about which one is appropriate for you.

Each fall and winter, cases of the flu begin to rise. Receiving the flu shot every year is an important way to protect yourself from becoming ill with the flu.

You can still get the flu vaccine if you have a mild illness, such as a cold or sinus infection. People who have a fever or a moderate or severe illness may need to delay vaccination until they’ve recovered.

If you’re sick and are unsure if you should receive a flu shot, talk to your doctor about your symptoms. They’ll be able to advise you on if it’s best to wait.