Influenza (Flu)

Influenza is caused by a family of viruses which strike in worldwide epidemics every year, usually between December and March. Despite the similarity in names, it is unrelated to either the stomach “flu” or “Haemophilus Influenzae Type B (HIB)”. Influenza is characterized by fever, cough, sore throat and generalized body-aches which last from 2-4 days. In normal healthy children & adults it is usually a self-limited, harmless illness, although it can sometimes be complicated or prolonged by pneumonia or dehydration. Such complications are far more frequent, and more serious, in individuals who are elderly OR who have certain severe chronic illnesses. These individuals are frequently hospitalized when they get Influenza, and complications may be fatal.

Influenza is a difficult germ to immunize against because it “changes it’s clothes” every year to fool the immune system. Each year it “looks” different to the immune system than the year before. Because of this, each year scientists must work hard to predict what the upcoming season’s Influenza will look like and make a new vaccine against it, different from the prior years. Likewise, people who need or want to be immunized against “the flu” will need to be re-immunized every year between September and December to be protected (depending on the year, sometimes the flu “hits” later in the winter than others, and in “late” years vaccination into January and February may still be effective).

The severity of Influenza also varies year-to-year. Some years it produces very mild symptoms, other years both the symptoms and the rate of complications can be much worse. Unfortunately it is even more difficult to predict in advance how severe a particular year’s flu will be than it is to design a vaccine against it. A particularly severe Flu seems to hit about once every 10-20 years. The flu of 1917 was the most severe in modern history, and caused many deaths. In November, 2003 there was a public panic – fueled by media hype – that the flu that year might be a similar “killer flu”. An earlier-than-usual start to the season and reports of several deaths among toddlers in Colorado started the panic. In the end the fears were over-blown. The children who died all had “risk factors” (see below) for influenza complications, and while the symptoms of the 2003 strain were slightly more severe than most years, the epidemic was also shorter than most years – lasting only about 6 weeks.

Ideally we would like to immunize everybody against Influenza every year, but until recently that was impossible. From the time the first influenza vaccines were developed (in the 1970’s) until very recently, there was always a shortage. In the United States from 1980-2007 the total doses made available each year fluctuated between 60-100 million. That was not enough to vaccinate our entire population of about 300 million, and if one subtracted out the elderly, in bad years it didn’t even leave enough for all the other high risk individuals (in good years it just barely did). So for all those years the standard recommendation of infectious disease experts and public health officials was that only high-risk patients should be vaccinated, and this policy of “rationing” was followed by most health care providers (including us). It took until 2008-9 before there was no shortage and no rationing policy needed.

Traditional injected Influenza vaccine is a purified, inactivated (killed) virus. When it was first produced in the 1970’s it was associated with a lot of side effects such as fevers and soreness that were almost as bad as Influenza itself, and there was a significant rate of severe allergic reaction especially in people with egg allergy. Today, however, the vaccine today is associated with very few side effects – just a small amount of redness or soreness at the site in 10-20% of people, and, in an even smaller percentage, a low grade fever. While serious allergic reactions still occasionally occur, they are much less common and no longer linked to egg allergy. The flu vaccine can be administered to children with egg intolerance, though for those with severe egg allergy we recommend they be immunized at their allergist’s office.





o All infants age 6-23 months, regardless of risk status (injected vaccine only in this age group).

o All patients 24 months and up who are on our “High-Priority Flu Vaccine list” or who meet the list criteria (either version of vaccine OK as long as no asthma or immune deficiency).


o Well children age 2-5y with no risk factors.

o Siblings or other family contacts of children on the high-priority list.


o All other children.



How do our providers decide who should be on the high-priority flu vaccine list each year? They look for kids who fall into one of the following categories or groups:

Epilepsy or Seizure Disorders, Metabolic Disorders (incl. Diabetes)

o Rationale: Influenza may worsen the underlying disease or throw it out of control (i.e. trigger severe seizures, diabetic coma, metabolic crises, etc.)

o This category does NOT include household contacts or patients with a history of simple febrile seizures.

Non-Ambulatory (wheelchair-bound) Patients or those with severe abnormalities of muscle tone and/or physical activity

o Rationale: impaired clearance of secretions from lungs increases risk of pneumonia.

o Includes: Cerebral Palsy, Rett Syndrome, Muscular Dystrophy, Spinal cord injury, and certain cases of global developmental delay, Meningomyelocele, birth defects, genetic syndromes.

o Does NOT include household contacts.

Significant Chronic Lung Disease

o Rationale: increased risk of pneumonia, Oxygen requirement, as well as exacerbation of underlying disease.

o Includes: Bronchopulmonary dysplasia, Cystic Fibrosis, Bronchiectasis, history of recurrent Pneumonias, and Asthma which is either persistent or moderate – severe.

o Does NOT include mild intermittent asthma (i.e. patients on “as needed” bronchodilators only with no need for controller meds nor any history of hospitalization) or household contacts.

Significant Heart Disease

o Rationale: increased demand on heart poses risk of heart failure.

o Includes: Hypoplastic Left Heart Syndrome, Transposition of the Great Vessels, Tetrology of Falot, and other “hemodynamically significant” congenital heart lesions.

o Does NOT include “hemodynamically insignificant” cardiac anomalies (e.g. small VSD’s) or household contacts.

Immune Deficiencies – 1°, 2°, congenital, acquired, & iatrogenic

o Rationale: impaired immunity increases duration & severity of influenza symptoms.

o Includes: Mild (Functional hypogammaglobulinemia, IgA, IgG subclass deficiencies, Cyclic Neutropenia, HIV, Uremia or renal failure on dialysis, insulin dependant diabeties)

o Includes: Severe (Agammaglobulinemia, SCIDS, CGD, AIDS, cancer chemotherapy, post transplant immune suppression, chronic steroid tx for any reason) AND their household contacts.

o Does NOT include household contacts of MILD group.