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Navigating flu season with PI

What is the flu?

Influenza, commonly known as "the flu," is a respiratory disease that usually comes on suddenly, with symptoms that vary from person to person. These symptoms may include aching muscles, sore throat, a dry cough, a runny or stuffy nose, fatigue, headache, a burning sensation in the chest, eye pain, sensitivity to light, and fever and/or chills (note that people with PI may not spike a fever).

Although many people think of the flu as harmless, from 2010-2020, the U.S. Centers for Disease Control and Prevention (CDC) estimates that between 12,000-52,000 people died of flu-related complications each year.

Colds, COVID-19, and the flu have overlapping symptoms but are different respiratory illnesses with different treatments, so it’s important to be tested if you feel sick. Note that it is also possible to get both COVID-19 and the flu at the same time.

Does PI put you at high risk for flu complications?

Except for those with interferon pathway deficiencies, people with PI are not necessarily at higher risk of developing complications from the flu unless they meet other high-risk criteria, such as: 

  • Being 5 years old or younger (especially younger than 2 years old). 
  • Being 65 years old or older.
  • Have asthma, diabetes, or chronic lung, heart, kidney, liver, metabolic, or blood conditions, including conditions that may be complications of PI.
  • Have had a stroke.
  • Have a secondary immunodeficiency caused by disease (e.g., HIV or blood cancer) or medication (e.g., immunosuppressive therapy).
  • Are pregnant.

The flu's most common complication is bacterial pneumonia, with other complications including viral pneumonia, myocarditis (inflammation of the heart muscle), and worsening of lung diseases. See a healthcare provider right away if you have:

  • Difficulty breathing, shortness of breath, or rapid, shallow breathing.
  • Blue-ish lips or nail beds.
  • Rapid pulse.
  • Chest or abdomen pain or pressure.
  • Seizures.
  • Signs of dehydration (not passing urine).
  • A persistent cough, especially if you’re coughing up colored phlegm or mucus (yellow/green).
  • Severe muscle pain, weakness, or unsteadiness.

Reye's syndrome is another flu complication that primarily affects children and causes severe vomiting and confusion. To decrease the chance of developing Reye’s syndrome, infants, children, and teenagers should not be given aspirin for fever reduction or pain relief.

What causes the flu and how does it spread?

The flu is caused by influenza viruses. The two main types that infect people, influenza A and influenza B, are genetically different. Influenza A can cause moderate to severe illness in all age groups and infects many species, including pigs, birds, and horses. Influenza B usually causes milder disease and primarily affects children. Both influenza A and influenza B strains cause seasonal outbreaks, typically during the fall and winter months in the U.S. Visit the CDC for this year’s flu season report.

Influenza A strains can also cause flu pandemics, like the 1918 flu and the swine flu in 2009. Pandemics happen when a new influenza A subtype, typically from animals, spreads in human populations that have not ‘seen’ the subtype before and have no immunity to it. Pandemic strains typically go on to become seasonal strains once the human population develops some immunity to them.

Influenza spreads through tiny airborne droplets created by coughing, sneezing, or talking, which can be inhaled or land on mucus membranes in the nose, mouth, or eyes. The flu can also be transmitted orally by kissing or by touching a surface contaminated with the virus and then touching your face. People with PI are equally at risk of contracting the flu as those without PI.

People with the flu are most contagious 1-2 days before symptoms appear and for 4-5 days after. The flu's incubation period is 1-4 days. While most people recover in a few days, some experience severe illness. 

How do you avoid the flu?

Get your yearly flu shot

An annual influenza vaccine is the most effective way to avoid getting seriously ill with the flu. Each year, the Advisory Committee on Immunization Practices (ACIP) at the CDC updates its recommendations for seasonal influenza vaccination. Because the vaccine changes every year to match circulating influenza virus strains, everyone 6 months of age or older needs a flu vaccine every year

Why should everyone be immunized? First, some people with PI may develop at least some antibodies or a T cell response, which is important for any viral infection, to the vaccine. Immunoglobulin (Ig) replacement therapy products (IVIG or SCIG) typically do not have protective levels of antibodies against current flu strains because manufacturing takes six months or more from the initial plasma donation. Second, household members of people with PI should get vaccinated to create a "protective cocoon" around the person with PI and decrease their exposure to the influenza virus. 

For the 2023-2024 season, all flu vaccines are quadrivalent, which means they protect against four different influenza virus strains, two influenza A and two influenza B strains. 

There are multiple types of flu vaccines available and selecting the right type is important. The inactivated or recombinant flu vaccine types are best for people with PI and their household members. People with PI and their household members should not receive the live attenuated flu vaccine. 

Additional recommendations from ACIP include:

  • People ages 65 or older should receive the high-dose inactivated, adjuvanted inactivated, or recombinant vaccine because these formulations provide greater protection in older individuals. 
  • Children 8 years old or younger who have either never been vaccinated for the flu or have only received one previous flu vaccine dose should be vaccinated with two doses of flu vaccine spaced four weeks apart.
  • Beginning with the 2023-2024 season, additional safety measures are no longer recommended for people who are allergic to eggs, regardless of the severity of previous allergic reactions. People with egg allergy may receive any vaccine (egg-based or non-egg-based) that is appropriate for their age and health status.
Inactivated and recombinant flu vaccines available for the 2023-2024 flu season.

The flu vaccine is safe and does not cause the flu, and individuals on Ig replacement therapy do not need to coordinate vaccine timing with their treatment. The vaccine is available from late summer, and the CDC recommends getting vaccinated in September or October for the best protection.

Stop the spread

Remember that flu vaccines are a crucial tool during respiratory virus season, but you should take advantage of other tools, too:

  • Regularly wash your hands with soap and water for 20 seconds, especially after coughing or sneezing. Hand sanitizer may not be as effective in killing the flu virus. 
  • Keep a distance of at least six feet from individuals who are sick. 
  • Use a well-fitted mask over your nose and mouth to avoid inhaling droplets that can spread respiratory viruses like influenza and COVID-19. During the 2020-2021 and 2021-2022 flu seasons, not many people got the flu because they were wearing masks for COVID-19 prevention, demonstrating that masks are effective against the transmission of both flu and COVID-19.
  • Try not to touch your nose, mouth, or eyes, as germs can spread this way. 
  • During flu season, those with PI should consider avoiding crowded indoor areas such as shopping malls.
  • When coughing or sneezing, cover your nose and mouth with a sleeve, elbow, or tissue. Dispose of the tissue after use. 
  • Stay home from work or school for 3-4 days after experiencing flu symptoms. 

What to do if you get the flu

People with PI should discuss plans with their healthcare provider about dealing with the flu before the season begins, including:

  • How and where will you get tested for influenza or other, similar respiratory viruses like COVID-19? 
  • What antiviral medication does your healthcare provider recommend and how will you get it? 
  • What symptoms should you pay particular attention to?

In case of illness, those with PI should immediately contact their healthcare provider to get tested for influenza and start antiviral treatment, which is most effective within 48 hours of symptoms appearing. There are no at-home rapid flu tests, but physicians' offices or pharmacies can quickly diagnose influenza.

What antiviral medications are available for the flu?

Antiviral medications for influenza work by preventing the virus from replicating and/or spreading. The same antiviral medicines that are effective for the general population are also effective for people with PI. 

There are four antiviral drugs approved by the U.S. Food and Drug Administration (FDA) and recommended by the CDC to treat the flu. All four work on both influenza A and influenza B viruses. Three of the antivirals are also recommended for the prevention of influenza (i.e., prophylactic use).

Available as a pill or liquid suspension and is FDA-approved for the treatment of flu within 48 hours of symptoms in people 14 days and older. The CDC also recommends prophylactic use in those ages 3 months and older.

A powder that is administered using an inhaler device and is approved for early treatment of flu in people 7 years and older. It is also approved for prophylactic use in people 5 years and older. Note that it is not recommended for people with breathing problems like asthma or COPD or those with milk protein or lactose allergies.

A single-dose pill approved for the treatment of flu within 48 hours of symptoms and as post-exposure prophylaxis (i.e., after known exposure to the flu, but before symptoms begin) in people 5 years and older. 

Given intravenously by a healthcare provider and is approved for early treatment of flu in people 2 years and older.

Antiviral treatment should be initiated in individuals with flu symptoms as soon as possible when there is known influenza activity in the community, even before they get tested for flu, especially for people at high risk of developing complications. For those with PI, antiviral medication can be given preventatively if a household member or other close contact becomes ill with the flu.

This page contains general medical and/or legal information that cannot be applied safely to any individual case. Medical and/or legal knowledge and practice can change rapidly. Therefore, this page should not be used as a substitute for professional medical and/or legal advice.