Table of ContentsView AllTable of ContentsFlu Shots When SickHow the Shot WorksWhen to Get ItWhen to PostponeWho Needs It MostWhen to Avoid It
Table of ContentsView All
View All
Table of Contents
Flu Shots When Sick
How the Shot Works
When to Get It
When to Postpone
Who Needs It Most
When to Avoid It
You can get a flu shot while sick if you have mild symptoms and no fever. Most healthcare providers feel it is best to get your flu shot early since it takes time to build immunity after you’ve received it. This means getting it when you have mild symptoms may be better than putting it off until you recover.
According to the Centers for Disease Control and Prevention (CDC), people who are moderately or severely ill should wait until they recover before getting vaccinated.This is because the flu shot is made of inactivated (dead) viruses that stimulate the production of protective antibodies. If you are really sick, your immune system will be less able to produce enough antibodies to protect against influenza A and B.
Verywell / Cindy Chung
What Happens When You Get a Flu Shot While Sick?
It is safe to get a flu shot if you have a mild cold with symptoms like a runny nose and a sore throat.
Being moderately or severely ill, however, temporarily weakens the immune system. If you’re sick when you get the flu shot, your immune system is already fighting the other illness or infection. This means it may not have the resources to also produce an immune response against the flu.
If you are ill, the flu shot could also slow your recovery from the other illness because your immune system is dividing its resources.
Older adults are more likely to respond poorly to getting a flu shot while sick because the immune response tends to weaken as you get older.This is also whyhigh-dose flu vaccinesare recommended for adults over 65.
How Does the Flu Shot Work?
Vaccinesare designed to stimulate a protective immune response. Theflu shotcontainsinfluenza (flu)viruses that have been killed. These are calledinactivated vaccines.
A person’s response to a vaccine may not always be strong enough to provide ample immune protection. Other things besides illness can undermine the response, such as undergoingchemotherapy, takingimmunosuppressants, or havinguntreated HIV. All these are associated with a weakened immune response.
What to Avoid After the Flu ShotMost people can continue their usual activities after a flu shot. If you are feeling nauseated, you may want to avoid eating certain foods that can make this side effect worse. Healthcare providers also recommend avoiding alcohol, which may suppress immune activity.
What to Avoid After the Flu Shot
Most people can continue their usual activities after a flu shot. If you are feeling nauseated, you may want to avoid eating certain foods that can make this side effect worse. Healthcare providers also recommend avoiding alcohol, which may suppress immune activity.
When Should You Get the Flu Shot?
Havingcold symptomsisn’t necessarily a reason to avoid the flu shot. Most people, even children, can get the shot if their symptoms are mild.
According to the CDC, it is perfectly fine to get a flu shot if you have:
What Is the Best Time of Year for a Flu Shot?To best protect you throughout the entire flu season, get the flu shot ornasal flu spray (FluMist)in September or October.
What Is the Best Time of Year for a Flu Shot?
To best protect you throughout the entire flu season, get the flu shot ornasal flu spray (FluMist)in September or October.
When to Postpone the Flu Shot
The is no clear line between when a sickness is “mild” or “moderate.” If you are unsure (or feel that your symptoms may be getting worse), err on the side of caution and delay vaccination until you feel better.
One of the main indications that you should postpone the flu shot is a moderate to high fever.In adults, this is generally when fever exceeds 102 F.
Severe diarrhea, vomiting, coughing up phlegm, or severe fatigue or malaise (a general feeling of unwellness) are also strong reasons for postponement.
If in doubt, call your healthcare provider or your child’s pediatrician for advice.
Who Needs the Flu Shot
Certain groups at high risk for flu complications should be vaccinated, This reduces the risk of complications likepneumonia,myocarditis(heart inflammation),encephalitis(brain inflammation),rhabdomyolysis(the destructive breakdown of muscle tissues), and multi-organ failure.
High-risk groups include:
Who Should Avoid the Flu Shot
As important as the flu shot is, it is not recommended for everyone. According to the CDC, flu vaccines should not be given to:
The CDC previously recommended that people with egg allergies get their flu vaccine in an inpatient or outpatient setting, but they no longer recommend any additional safety measures for people with egg allergies, regardless of severity.
Some people with a history of a severe paralyzing illness calledGuillain-BarréSyndrome (GBS)should alsonot get a flu vaccine. Talk to your healthcare provider before getting vaccinated if you have had GBS.
Summary
You don’t need to postpone your flu shot for a mild illness. If you have a high fever or moderate to severe illness with or without a fever, however, delay vaccination until you’ve recovered. If in doubt, contact your healthcare provider.
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12 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.Influenza (flu) vaccine.Ohio State University, BuckMD Blog.Can I get the flu shot if I’m sick? What if I have a fever?Castrucci MR.Factors affecting immune responses to the influenza vaccine,Hum Vaccin Immunother.2018;14(3):637–46. doi:10.1080/21645515.2017.1338547Centers for Disease Control and Prevention.Understanding how vaccines work.Centers for Disease Control and Prevention.Understanding how vaccines work.Harvard T.H. Chan School of Public Health.Nutrition and immunity.Centers for Disease Control and Prevention.Vaccines when your child is sick.Grohskopf LA, Blanton LH, Ferdinands JM, et al.Prevention and control of seasonal influenza with vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2022–23 influenza season.MMWR Recomm Rep2022;71(No. RR-1):1–28. doi:10.15585/mmwr.rr7101a1.Musana KA, Yale SH, Mazza JJ, Reed KD.Practical considerations to influenza vaccination.Clin Med Res.2014;2(4):256–9. doi:10.3121/cmr.2.4.256Centers for Disease Control and Prevention.Flu symptoms & complications.Centers for Disease Control and Prevention.Who should and who shouldn’t get a flu vaccine.Centers for Disease Control and Prevention.Flu Vaccine Safety Information.
12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.Influenza (flu) vaccine.Ohio State University, BuckMD Blog.Can I get the flu shot if I’m sick? What if I have a fever?Castrucci MR.Factors affecting immune responses to the influenza vaccine,Hum Vaccin Immunother.2018;14(3):637–46. doi:10.1080/21645515.2017.1338547Centers for Disease Control and Prevention.Understanding how vaccines work.Centers for Disease Control and Prevention.Understanding how vaccines work.Harvard T.H. Chan School of Public Health.Nutrition and immunity.Centers for Disease Control and Prevention.Vaccines when your child is sick.Grohskopf LA, Blanton LH, Ferdinands JM, et al.Prevention and control of seasonal influenza with vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2022–23 influenza season.MMWR Recomm Rep2022;71(No. RR-1):1–28. doi:10.15585/mmwr.rr7101a1.Musana KA, Yale SH, Mazza JJ, Reed KD.Practical considerations to influenza vaccination.Clin Med Res.2014;2(4):256–9. doi:10.3121/cmr.2.4.256Centers for Disease Control and Prevention.Flu symptoms & complications.Centers for Disease Control and Prevention.Who should and who shouldn’t get a flu vaccine.Centers for Disease Control and Prevention.Flu Vaccine Safety Information.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Centers for Disease Control and Prevention.Influenza (flu) vaccine.Ohio State University, BuckMD Blog.Can I get the flu shot if I’m sick? What if I have a fever?Castrucci MR.Factors affecting immune responses to the influenza vaccine,Hum Vaccin Immunother.2018;14(3):637–46. doi:10.1080/21645515.2017.1338547Centers for Disease Control and Prevention.Understanding how vaccines work.Centers for Disease Control and Prevention.Understanding how vaccines work.Harvard T.H. Chan School of Public Health.Nutrition and immunity.Centers for Disease Control and Prevention.Vaccines when your child is sick.Grohskopf LA, Blanton LH, Ferdinands JM, et al.Prevention and control of seasonal influenza with vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2022–23 influenza season.MMWR Recomm Rep2022;71(No. RR-1):1–28. doi:10.15585/mmwr.rr7101a1.Musana KA, Yale SH, Mazza JJ, Reed KD.Practical considerations to influenza vaccination.Clin Med Res.2014;2(4):256–9. doi:10.3121/cmr.2.4.256Centers for Disease Control and Prevention.Flu symptoms & complications.Centers for Disease Control and Prevention.Who should and who shouldn’t get a flu vaccine.Centers for Disease Control and Prevention.Flu Vaccine Safety Information.
Centers for Disease Control and Prevention.Influenza (flu) vaccine.
Ohio State University, BuckMD Blog.Can I get the flu shot if I’m sick? What if I have a fever?
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Centers for Disease Control and Prevention.Understanding how vaccines work.
Harvard T.H. Chan School of Public Health.Nutrition and immunity.
Centers for Disease Control and Prevention.Vaccines when your child is sick.
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Musana KA, Yale SH, Mazza JJ, Reed KD.Practical considerations to influenza vaccination.Clin Med Res.2014;2(4):256–9. doi:10.3121/cmr.2.4.256
Centers for Disease Control and Prevention.Flu symptoms & complications.
Centers for Disease Control and Prevention.Who should and who shouldn’t get a flu vaccine.
Centers for Disease Control and Prevention.Flu Vaccine Safety Information.
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