Why Does Flu Affect Some People More Than Others?

Sep 5, 2022

Certain people may have higher risk factors for complications from influenza

No matter what age—or how healthy you may be—you can catch influenza. However, some people may be more apt to have complications from the flu, which may range from ear and sinus infections to worsening of certain ongoing medical conditions, like diabetes or asthma.

Younger or older ages are risk factors

According to the Centers for Disease Control and Prevention (CDC), while anyone who gets influenza can develop serious problems due to the flu, there are certain age groups who may be at higher risk for these issues. These include the very young (including children younger than 5 years, but especially those who are under 2 years old), as well as people aged 65 years and older.

Notably, older people are at risk in part because the immune system becomes weaker with age. An immune system that's weakened due to age may reduce older people's ability to have a full response to a standard-dose flu vaccine. In addition, older people are also predisposed to have other health issues, such as diabetes, that may increase their risk for flu complications. Estimates have suggested that between 50% and 70% of those who have been hospitalized due to influenza were older than 65.

No matter what age you are—or how healthy you may be—you can catch influenza.

Pre-teen getting flu shot at clinic with her dad present

Certain health considerations are risk factors

In addition to age, several health-related conditions may increase the chance of serious flu complications, including:

Blood, endocrine, liver and metabolic disorders: Examples include sickle cell disease and diabetes
Chronic lung disease: Examples include chronic obstructive pulmonary disease (COPD) and cystic fibrosis
Kidney diseases
History of stroke or heart disease: Examples include congestive heart failure and coronary artery disease
Asthma
Neurologic and neurodevelopment conditions
Higher body mass index (BMI): BMI of 40 and above
Long-term use of aspirin- or salicylate-containing medications: Within people aged 19 years old or younger
Immunocompromised status: May be due to disease (such as HIV or some cancers) or due to certain types of medical treatment (such as chemotherapy, radiation or chronic corticosteroid usage)

Other factors that may put people at higher risk for serious flu complications are being pregnant or 2 weeks postpartum, and living in a nursing home or other long-term care facility.

Flu complications also tend to be higher in people of certain racial or ethnic groups, including Blacks, American Indians or Alaskan Natives, Hispanics and Latinos. Severe flu outcomes, including flu-associated hospitalization, ICU admission, and in-hospital death, have been shown to occur at greater rates in these people when compared to non-Hispanic Whites.

Flu vaccination protects the vulnerable

Even if you do not have any of these risk factors, getting your flu vaccine may help protect people at risk of complications that can result from influenza. Vaccination, along with hygienic habits, can go a long way in reducing the impact of influenza in your community.

Learn more about preventing flu spread