Who is at high risk for flu complications?

Why some people get sicker from flu

Flu (influenza) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death (CDC). Most people recover in a few days to less than two weeks, but some develop complications such as pneumonia, sinus and ear infections, inflammation of the heart, brain or muscles, sepsis, or a worsening of a long-term condition, for example an asthma attack (CDC).

Serious problems can happen to anyone at any age, even healthy people (CDC). But the risk is not spread evenly. During recent flu seasons, 9 out of 10 people hospitalized with flu had at least one underlying health condition (CDC).

The CDC list of people at higher risk

CDC lists these groups as being at increased risk of serious flu complications (CDC):

By age

• Adults 65 years and older
• Young children. All children younger than 5 are considered at higher risk. The highest risk is for those younger than 2, with the highest hospitalization and death rates among infants younger than 6 months.
• Children and teens younger than 19 on long-term aspirin or salicylate medicines

By health condition

• Asthma
• Chronic lung disease, such as COPD and cystic fibrosis
• Heart disease, such as congenital heart disease, congestive heart failure and coronary artery disease
• Endocrine disorders, such as diabetes
• Kidney disorders
• Liver disorders
• Blood disorders, such as sickle cell disease
• Metabolic disorders, such as inherited metabolic and mitochondrial disorders
• Neurologic and neurodevelopmental conditions
• Having had a stroke
• A body mass index (BMI) of 40 or higher
• A weakened immune system, from a disease (such as HIV or some cancers like leukemia) or from medicines (such as chemotherapy, radiation for cancer, long-term corticosteroids or other drugs that suppress the immune system)
• Certain disabilities, especially when they make it hard to use muscles, breathe, cough, swallow or clear fluids from the airways

Other people at higher risk

• Pregnant women, including up to 2 weeks after the end of pregnancy
• People who live in nursing homes and other long-term care facilities
• Some racial and ethnic groups. CDC says non-Hispanic Black, Hispanic or Latino, and American Indian or Alaska Native people are at increased risk of hospitalization with flu.

The vaccine advisory committee (ACIP) uses a very similar list for deciding who should come first when vaccine supply is short. Two differences: it puts all adults aged 50 and older in that list, and it lists chronic heart disease but excludes high blood pressure on its own (ACIP 2024). Its newer report keeps those groups unchanged (ACIP 2025).

If you live with or care for someone in these groups, your own vaccination matters too. ACIP puts emphasis on vaccinating household contacts and caregivers of high-risk people, particularly contacts of babies younger than 6 months, who are too young for a flu vaccine (ACIP 2024).

Emergency warning signs

CDC says people with these warning signs should get medical care right away (CDC). The lists are not complete, so get care for any other symptom that is severe or worrying.

In children:

• Fast breathing or trouble breathing
• Bluish lips or face
• Ribs pulling in with each breath
• Chest pain
• Severe muscle pain (child refuses to walk)
• Dehydration (no urine for 8 hours, dry mouth, no tears when crying)
• Not alert or interacting when awake
• Seizures
• Fever above 104 F that is not controlled by fever-reducing medicine
• In children younger than 12 weeks, any fever
• Fever or cough that improve but then return or worsen
• Worsening of chronic medical conditions

In adults:

• Difficulty breathing or shortness of breath
• Persistent pain or pressure in the chest or abdomen
• Persistent dizziness, confusion, or not being able to wake up
• Seizures
• Not urinating
• Severe muscle pain
• Severe weakness or unsteadiness
• Fever or cough that improve but then return or worsen
• Worsening of chronic medical conditions

Common flu symptoms, which usually come on suddenly, are fever or feeling feverish and chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches and tiredness. Not everyone with flu has a fever (CDC).

Antiviral treatment: why high-risk people should call early

CDC recommends early treatment, as soon as possible, for people who have flu or suspected flu and are at higher risk of serious complications, such as people with asthma, diabetes or heart disease (CDC). What CDC says about these medicines (CDC):

• They are prescription medicines (pills, liquid, an inhaled powder or an IV), not sold over the counter, and they are different from antibiotics.
• They work best when started within two days after symptoms begin, and can lessen symptoms and shorten the time you are sick by about a day. They might also prevent some complications, like pneumonia.
• Starting later can still help, especially for someone with a higher-risk condition or who is very sick, for example in the hospital.
• Most people who are not at increased risk do not need antiviral treatment.

Vaccination

CDC says everyone 6 months and older should get a flu vaccine every season, with rare exceptions, and that vaccination is particularly important for people at higher risk of serious complications (CDC). For people with certain chronic health conditions, a flu vaccine has been shown to reduce the risk of flu-related worsening of those conditions and to prevent flu-associated hospitalization (CDC).

• When: September or October is ideal for most people who need one dose. Vaccination should continue after October for as long as flu is circulating (ACIP 2025). Protection takes about two weeks to develop (CDC).
• Adults 65 and older: a high-dose, recombinant or adjuvanted flu vaccine is preferred. If none of these is available, any other flu vaccine approved for your age should be used (ACIP 2025).
• Pregnancy: if you are pregnant or have certain chronic health conditions, CDC says to get a flu shot. The nasal spray vaccine is not for pregnant people (CDC). Vaccination in the third trimester has been linked in several studies with less flu illness in babies in their first months after birth (ACIP 2025).
• Children 6 months through 8 years who have not had at least 2 flu vaccine doses before July 1, 2025, or whose history is unknown, need 2 doses this season, at least 4 weeks apart (ACIP 2025).

Recommendations can change from season to season. Your doctor, pharmacist or your child's doctor can tell you which vaccine fits you now.

Common questions

Is high blood pressure a flu risk factor?

Not on its own in ACIP's list, which covers heart and blood vessel disorders but excludes isolated high blood pressure (ACIP 2024). Heart disease such as heart failure or coronary artery disease is on CDC's list (CDC).

I am healthy and under 65. Do I need to worry?

Serious flu can happen to healthy people too, but most people not at increased risk who get flu do not need antiviral drugs and can recover at home (CDC). Watch for the warning signs above, and the vaccine is still recommended for you (CDC).

How long after pregnancy does the higher risk last?

CDC counts pregnant women as higher risk up to 2 weeks after the end of pregnancy (CDC).

Related guides: pneumonia risk factors, RSV risk factors, shingles risk factors, measles risk factors and COPD risk factors.