Influenza Vaccine (Flu Shot and Nasal Spray) for Adults

Medically Reviewed by Nayana Ambardekar, MD on March 15, 2023
5 min read

The influenza vaccine is a yearly vaccine that protects you from getting the flu, a viral respiratory illness that spreads very easily. The flu can lead to serious health complications and possibly death.

The best way to prevent the flu is to get vaccinated. There are a few types of flu vaccines:

  • Flu shot: The flu shot is typically given to people six months and older. It is an inactive vaccine, which means it is made using a dead form of the viruses the shot protects against. The dead germs cannot make you sick. Those ages 18 to 64 can opt for an intradermal flu shot. This injection uses a smaller needle and goes into the top layer of the skin instead of the muscle. The vaccines are generally safe for those with egg allergies. If you have severe allergies you should get the flu shot from a doctor who can treat a severe allergic reaction -- either at your doctor's office, a hospital, a clinic, or a health department.
  • Fluzone high dose: This inactivated vaccine was developed for those ages 65 and older, because older people have weaker immune systems. It's preferred for this group instead of a regular flu shot when available.
  • Egg-free vaccines: Unlike most flu vaccines, these are not grown inside eggs. They're approved for people with a severe allergy to eggs.
  • Nasal spray: The nasal spray flu vaccine is a live attenuated vaccine, or LAIV. Unlike the flu shot, it is made from live, but weakened, influenza viruses. However, you cannot get the flu from the nasal spray vaccine. Healthy, non-pregnant people ages 2 to 49 may receive the nasal spray. 

The three or four flu strains covered by the flu vaccine differ from year to year. That’s because the flu viruses are constantly changing. Scientists develop a new flu vaccine each season based on research that predicts which strains will be most likely to make you sick. 

Flu seasons also vary, depending on where you live. Flu season can run from October to May. You should get vaccinated as soon as the vaccine becomes available. It takes about two weeks for the flu vaccine to start working, so you want to make sure you are fully protected as soon as possible. Generally, the seasonal flu vaccine is available from September until spring.

The CDC recommends that most every adult receive a flu vaccine every year, especially those who are at high risk for developing flu-related complications and those who care for or live with such people, such as health care workers.

You are more likely to develop serious flu-related complications and should get a flu vaccine if you have:

Your risk of developing flu-related complications is also increased if you are:

  • Older than age 50 or younger than age 2
  • Pregnant
  • American Indian or Alaskan Native

You should also get a flu vaccine if you live in a nursing home or other long-term care facility.

You should NOT get the influenza vaccine if you:

  • Developed Guillain-Barre syndrome within six weeks of receiving the flu vaccine in the past
  • Had a severe reaction to the flu vaccine in the past
  • Have a severe allergy to any vaccine component

It's long been advised that people with allergies to eggs should not get the flu shot. However, the American College of Allergy, Asthma and Immunology says the vaccine contains such a low amount of egg protein that it's unlikely to cause an allergic reaction in those with an egg allergy. If you have a severe egg allergy (anaphylaxis), talk to your doctor before getting the flu vaccine. Also, as mentioned above, flu vaccines not made with eggs are available.

The nasal spray flu vaccine can only be used in healthy, younger adults who are not pregnant. In addition to the previously listed adults who should not receive the flu shot, adults should NOT get the nasal spray influenza vaccine if they:

  • Are pregnant
  • Are ages 50 or older 
  • Have a weakened immune system due to disease or certain medical treatments
  • Have a long-term health condition, such as diabetes, kidney disease, or heart or lung disease, including asthma
  • Have a muscle or nerve condition that can cause problems with breathing or swallowing (such as epilepsy or cerebral palsy)
  • Have a weakened immune system
  • Have a nasal condition that could make breathing difficult

You should not get the nasal spray flu vaccine if you are in contact with people who have a severely weakened immune system.

If you are moderately to severely ill, your doctor may recommend waiting to get the shot until after you recover. The CDC says you can still get the vaccine if you have a mild illness such as a cold or low-grade fever.

If you have a stuffy nose, your doctor may recommend that you wait to get the nasal spray flu vaccine, or get the flu shot instead.

Like all medications, vaccines can have side effects. But the risk of harm or death from the influenza vaccine is rare.

The flu shot and nasal spray can cause different types of side effects.

Flu shot side effects may include:

  • Low fever
  • Muscle aches
  • Soreness, redness, or swelling where the shot was given

The nasal spray flu vaccine for adults may cause:

Although it's rare, someone may have a severe allergic reaction to an ingredient in the vaccine. Most of the time, such reactions occur within a few minutes to a few hours of receiving the vaccine. The following can be signs of a severe allergic reaction:

Seek immediate medical care if you notice any of these signs after receiving the influenza vaccine.