You are here

The following includes information regarding influenza and primary immunodeficiency diseases (PI). 

Influenza Disease

Typical influenza disease is characterized by abrupt onset of fever or feeling feverish/chills, aching muscles, sore throat, and non-productive cough. Additional symptoms may include runny or stuffy nose, fatigue, headache, a burning sensation in the chest, eye pain and sensitivity to light. Typical influenza disease does not occur in every infected person. Someone who has been previously exposed to similar virus strains (through natural infection or vaccination) is less likely to develop serious clinical illness. Although many people think of influenza as the “flu” or just a common cold, it is really a specific and serious respiratory disease that can result in hospitalization and death.

Flu and the common cold are both respiratory illnesses, but they are caused by different viruses. Because these two types of illnesses have similar symptoms, it can be difficult to tell the difference between them based on symptoms alone. Cold symptoms are usually milder than the symptoms of flu. People with colds are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems such as pneumonia, bacterial infections, or hospitalizations. In general, flu is worse than the common cold, and symptoms are more common and intense. Flu can have very serious associated complications.

Because colds and flu share many symptoms, it can be difficult (or even impossible) to tell the difference between them based on symptoms alone. Special tests that usually must be done within the first few days of illness can tell if a person has the flu.

Image from Centers for Disease Control and Prevention, Cold Versus Flu:

The most frequent complication of influenza is bacterial pneumonia. Viral pneumonia is a less common complication but has a high fatality rate. Other complications include inflammation of the heart and worsening of pulmonary diseases (e.g., bronchitis). Reye’s syndrome is a complication that occurs almost exclusively in children—patients suffer from severe vomiting and confusion, which may progress to coma because of swelling of the brain. To decrease the chance of developing Reye’s syndrome, infants, children, and teenagers should not be given aspirin for fever reduction or pain relief.

Viruses cause influenza. There are two basic types, A and B, which can cause clinical illness in humans. Their genetic material differentiates them. Influenza A can cause moderate to severe illness in all age groups and infects humans and other animals. Influenza B usually causes milder disease and affects only humans, primarily children.

Subtypes of the type A influenza virus are identified by two antigens on the surface of the virus. These antigens can change, or mutate, over time. When a “shift” (major change) occurs, a new influenza virus is born, and an epidemic is likely among the unprotected population. This happened when the novel H1N1 influenza virus appeared in March of 2009 and led to a major pandemic, lasting thru the summer of 2010.

Influenza is transmitted from person to person by tiny airborne droplets formed during coughing and sneezing. These droplets are inhaled or land on mucus membranes (lining of the nose or inside of the mouth or the conjunctiva). Influenza virus also can be transmitted orally most commonly by kissing or by touching a surface or object that has flu virus on it and then touching their own mouth, nose or possibly their eyes.

A person is most likely to pass on the virus during the period beginning one to two days before the onset of symptoms and ending four to five days after the onset. The incubation period of influenza is usually two days but can range from one to four days. For most people, the flu lasts only a few days, but some people get much, much sicker. Influenza is of particular concern in people with pre-existing heart and/or lung conditions, the elderly, children under 2 years of age, pregnant women and persons with impaired immune systems.

(return to top of page)


Vaccination is the principal means of preventing influenza and its complications. Here are some additional steps that may help prevent the spread of respiratory illnesses like influenza:

  • Cover your nose and mouth with your sleeve or a tissue when you cough or sneeze—throw the tissue away after you use it.
  • Wash your hands often with soap and water, especially after you cough or sneeze. If you are not near water, use an alcohol-based hand cleaner. However, hand sanitizer has been found to be ineffective in killing the influenza virus contained in wet/moist mucus. For with contact to that form of virus carrier, washing with water, with or without soap, is the more effective way to kill the influenza virus.
  • Stay away as much as you can from people who are sick.
  • If you get influenza, stay home from work or school for at least 24 hours after the fever has ended. If you are sick, don’t go near other people to avoid infecting them.
  • Try not to touch your eyes, nose, or mouth. Germs often spread this way.

(return to top of page)


The most effective way to avoid an infection with influenza is to receive the influenza vaccine annually. Influenza vaccines are safe and effective, and, contrary to a common misconception, they do not cause the flu. Because the influenza virus characteristically changes or mutates from year to year, each year it is necessary to prepare a new vaccine for protection from the new flu strains that are present that year. For this reason it is essential that everyone get immunized against the seasonal flu every year because last year’s vaccine may not be protective against this year’s virus strains. Also, the protection given by the vaccine can wane over time so that last year’s vaccination may not continue to be protective, particularly for individuals age 65 and older.

(return to top of page)

Flu Vaccine Protection 202020—What Is Best for You?

The latest update from the Advisory Committee on Immunization Practices (ACIP) of the CDC is now published. Here is why it matters.

Each year, ACIP updates its recommendations for seasonal influenza vaccination. Everyone six months of age or older needs vaccination every year. That hasn't changed. However, the antigenic formulation for 2019-2020 vaccine differs from the 2018-2019 vaccine. All flu vaccines have been updated to better match circulating viruses. The influenza A (H3N2) and the A (H3N2) components were updated. There were no changes in the influenza B virus component from last year’s vaccine.

"No preferential recommendation is made for one influenza vaccine product over another for persons for whom more than one licensed, recommended, and appropriate product is available."

Another significant note of particular interest to children and their parents is that FluMist nasal spray vaccine is also available this year. This vaccine is a quadravalent live attenuated influenza vaccine (LAIV4).

No flu season is the same. It is impossible to predict when flu season will peak. We have lots of people to vaccinate—everyone 6 months and older—and there is a plethora of flu vaccine choices but only three classes of flu vaccine.

1. Inactivated Influenza Vaccine (IIV)

First, the inactivated influenza vaccine (IIV), available as:

  • The standard flu shot in trivalent (IIV3) and quadravalent versions (IIV4);
  • A high-dose version only for seniors 65 years or older (HD-IIV3); and
  • A cell-cultured version (CCIIV) for adults of all ages.

As recommended last year, “individuals with a history of egg allergy of any severity may receive any licensed, recommended, and age-appropriate influenza vaccine (IIV, RIV4, or LAIV4)."

2. Recombinant Influenza Vaccine

Next, one of the newer flu vaccines on the market: the recombinant influenza vaccine (brand name Flublok®). This is totally egg-free and can be given to patients aged 18-49 years, including those with egg allergy of any severity.

3. Live Attenuated Influenza Vaccine

And finally, the live attenuated influenza vaccine, abbreviated LAIV4. It is made from live but weakened virus. It is only for healthy people aged 2-49 years, as long as they are not pregnant. ACIP now recommends LAIV for healthy children aged 2-8 years. There is a qualifier. Flu vaccination should not be delayed. If LAIV is not immediately available, it is fine to vaccinate with IIV, the inactivated vaccine.

Some people should not be given the nasal spray flu vaccine:

  • Children younger than 2 years
  • Adults 50 years and older
  • Pregnant women
  • People with a history of severe allergic reaction to any component of the vaccine or to a previous dose of any influenza vaccine
  • Children 2 years through 17 years of age who are receiving aspirin- or salicylate-containing medications.
  • Children 2 years through 4 years who have asthma or who have had a history of wheezing in the past 12 months.
  • People who have taken influenza antiviral drugs within the previous 48 hours.
  • People who care for severely immunocompromised persons who require a protected environment (or otherwise avoid contact with those persons for 7 days after getting the nasal spray vaccine).
  • Children and adults who are immunocompromised due to any cause (including immunosuppression caused by medications or by HIV infection).

There is no reason to expect that FluMist poses any risk for people with Chronic Granulomatous Disease (CGD) or complement disorders and probably for any but the most severe primary immunodeficiency disease. Nevertheless, the ACIP guidelines still recommend that all individuals with immunocompromise not be given LAIV.

(return to top of page)

Primary Immunodeficiency Family Plan

For families with a member who has a primary immunodeficiency disease (PI), we recommend that all members of the family should be given the inactivated (killed) vaccine. The vaccines usually become available in August or September. Studies have shown that immunization can still be effective when given well into February or March in some years, so it is important to ask for the vaccine even if the New Year has passed.

Why do we recommend that everyone be immunized? First, some people with PI may benefit from the vaccine. Even if they do not, there is little down side to receiving the inactivated vaccine. Family members who are able to respond to the vaccine will be protected. Even if the person with PI does not respond to the immunization, he or she will benefit from having everyone else in the family protected from infection and not susceptible to bringing the virus home with them. We want to create a “protective cocoon” of immunized persons surrounding our patients so that they have less chance of being exposed. It would be a good strategy to encourage employers to provide influenza immunization programs at the place of work and schools to similarly encourage immunization of the student body to further extend this “cocoon.”

Individuals with PI have the same risk of contracting flu as does the rest of the population. The same type of anti-viral medicine, i.e., Tamiflu or Relenza, which is effective for people with normal immune systems, would be effective for people with PI who get influenza. Note that Ig replacement therapy may not protect against newly emerged strains of the influenza virus since the Ig contained in the currently available lots of IVIG or SCIG was obtained from donors several months ago, probably before the newer strains of influenza had circulated thru the donor population to result in antibody formation.

Influenza can be diagnosed rapidly by a test done in physician offices. If the test is positive, it is recommended that persons immediately begin anti-virus treatment. Speed is important in this situation since the antiviral medications are most effective if begun within 48 hours of the onset of the illness. It would be a good idea to discuss with your physician plans for dealing with influenza before you get sick so that you are prepared. If you do become ill, you should contact your doctor immediately about initiating treatment. However, it would be wise to contact your physician first, before going to their office, an urgent care facility or emergency room.

During the flu season, you may want to stay away from crowded public places, such as shopping malls, if you are concerned about exposure. Most people can get information from the national media and from their physicians on other ways to prevent exposure, as well as when to use additional precautionary measures.

(return to top of page)

What Do I Do If There Is Influenza in the Schools or at My Workplace?

There is no single recommendation that is applicable to every situation. Some medical advisors recommend that unless influenza is in their classroom children with PI should go to school. If there is a known direct contact with secretions from a flu-affected child or adult by the individual with PI, some medical advisors suggest that the patient should go on Tamiflu once a day for 10 days. If the individual with PI develops symptoms of influenza, that person should be treated with Tamiflu twice a day for 5 days. Relenza could also be used as the anti-viral treatment. The same treatment recommendations should apply to adults with Common Variable Immune Deficiency (CVID) or other types of PI. As stated earlier, only people with the most severe forms of PI, such as babies with untreated Severe Combined Immunodeficiency (SCID), need to strictly avoid contact with individuals recently immunized with FluMist. If you have any questions, please contact your specialist.

(return to top of page)


There are four FDA-approved antiviral drugs recommended by CDC to treat flu this season.

  • Oseltamivir phosphate (available as a generic version or under the trade name Tamiflu®)
  • Zanamivir (trade name Relenza®)
  • Peramivir (trade name Rapivab®)
  • Baloxavir marboxil (trade name Xofluza®)

Generic oseltamivir and Tamiflu® are available as a pill or liquid suspension and are FDA approved for early treatment of flu in people 14 days and older. Zanamivir is a powder that is inhaled and approved for early treatment of flu in people seven years and older. (Note: Zanamivir, trade name Relenza®, is administered using an inhaler device and is not recommended for people with breathing problems like asthma or COPD.) Peramivir is given intravenously by a health care provider and is approved for early treatment of flu in people two years and older. Baloxavir is a pill given as a single dose by mouth and is approved for early treatment of flu in people 12 years and older. (Note: Baloxavir, trade name Xofluza®, is not recommended for pregnant women, breastfeeding mothers, outpatients with complicated or progressive illness, or hospitalized patients because there is no information about the use of baloxavir in these patients.)

The CDC notes that Neuraminidase inhibitor (NAI) antivirals have been effective in randomized trials but have been underused with both outpatients and inpatients. The 2019-2020 season CDC advisory reminds clinicians that all inpatients and all high-risk patients (whether inpatient or outpatient) who are suspected of having or confirmed to have influenza should be treated. Because of the importance of early treatment, decisions about starting antiviral treatment should not wait for laboratory confirmation of influenza. Therefore, empiric antiviral treatment should be initiated in symptomatic individuals as soon as possible when there is known influenza activity in the community.

Those groups include the following:

  • Patients with severe, complicated, or progressive illness, including outpatients with severe or prolonged progressive symptoms or those who develop pneumonia;
  • Children under age 2 years or people 65 years and older, as well as people younger than 19 years who are receiving long-term aspirin therapy;
  • American Indians/Alaska natives;
  • Women who are pregnant or within 2 weeks postpartum;
  • People with suppressed immune systems;
  • Extremely obese people (body mass index of at least 40); and
  • Those living in long-term care facilities.

Treatment is also indicated when flu is suspected or confirmed for “persons with chronic pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, hematological (including sickle cell disease), and metabolic disorders (including diabetes mellitus), or neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy [seizure disorders], stroke, intellectual disability [mental retardation], moderate to severe developmental delay, muscular dystrophy, or spinal cord injury),” the CDC advises.

A history of current season influenza vaccination does not exclude a diagnosis of influenza in an ill child or adult. During influenza season especially, high-risk patients should be advised to call their provider promptly if they have symptoms of influenza. To facilitate early initiation of treatment, when feasible, an antiviral prescription can be provided without testing and before an office visit. Three NAIs are approved by the US Food and Drug Administration and recommended for the 2019-2020 season: oseltamivir (Tamiflu®), zanamivir (Relenza®); and peramivir (Rapivab®).

For more, updated information on the flu, visit the CDC website:

(return to top of page)

Revised October 2019