Viral influenza infections continue to be responsible for significant morbidity and mortality worldwide. In the United States alone, an average of 20,000 flu-related deaths occur annually and estimates of the economic loss range from $3 billion to $5 billion each year, and reach as high as $12 billion.

The flu is a respiratory disease and generally spreads from person-to-person when an infected person coughs or sneezes. While certain high-risk groups are especially vulnerable (the very young, people with chronic medical conditions such as asthma and chronic obstructive pulmonary disease, pregnant women and the immunocompromised), the flu can cause severe illness and life-threatening complications in any age group.

The primary prevention for the flu in any season is vaccination. The licensed vaccine used in the United States is made of inactivated or killed influenza viruses and cannot cause influenza infection or illness. Effectiveness of vaccination has been shown to be 70-90 percent prevention of illness in healthy adults. Onset of this protection occurs within one to two weeks of vaccination. The primary side effects include soreness and swelling at the site of injection. A less common side effect would be mild fever and body aches for one to two days. Allergic reactions are rare but may occur in people with severe allergy to eggs.

A number of antiviral agents, including amantadine, rimantadine, zanamivir and oseltamivir, are available for treatment of acute, uncomplicated influenza; however, they are not a substitute for vaccination. Their spectrum of coverage, dose, routes of administration and other details of use vary from drug to drug but all require administration prior to or early into the onset of the flu. Any substantial delay reduces their efficacy considerably.

Current Situation
For the current flu season, the vaccine will be a trivalent combination of A/Panama, A/New Caledonia and B/Yamanashi. Two of these strains are new to the vaccine this year. Unfortunately, a lower-than-anticipated production yield of this year’s vaccine has led to substantial delays in vaccine distribution. While the total amount of influenza vaccine manufactured this year will be close to the amount manufactured last year, most of the vaccine will not be available until November, and the final vaccine lots will not be released until early December. This will have potential effects on this year’s influenza season.

In response to this, the Centers for Disease Control and Prevention (CDC) have developed recommendations specific to this flu season. Details of these recommendations can be found at the Web sites noted in this article but some key elements are summarized here.

• When influenza vaccine becomes available, vaccination efforts should be focused on people at high risk for complications associated with influenza disease and on health-care personnel working with them. People at high risk are:

1. Individuals older than 65;
2. Residents of nursing homes and other chronic-care facilities that house people of any age who have chronic medical conditions;
3. Children and adults who have chronic disorders of the pulmonary or cardiovascular systems, including asthma;
4. Children and adults who required regular medical follow-up or hospitalization during the preceding year because of chronic metabolic diseases (including diabetes mellitus), renal dysfunction, hemoglobinopathies, or immunosuppression (for example, caused by medications or human immunodeficiency virus);
5. People aged 6 months to 18 years who are receiving long-term aspirin therapy and, therefore, might be at risk for developing Reye syndrome after influenza; and
6. Women who will be in the second or third trimester of pregnancy during the influenza season.

• Implementation of organized mass influenza vaccination campaigns should be delayed until November.
• Immunization efforts should continue into December, especially for high-risk persons remaining unimmunized.

Role of the Provider
In the face of delayed vaccine availability, providers must include both continued support of vaccination as an essential form of disease prevention as well as careful planning of the timing of vaccinations during this year’s influenza season. While the best time to vaccinate is in October or November, shots can be given any time during flu season. Good preparation by providers will reduce patient frustration and ensure that comprehensive vaccination will be achieved.

Resources for Current Information
CDC Influenza Web sites:

This article was prepared with the guidance of Dr. Tim Albertson, DUR Board member and Chief, Department of Pulmonology, University of California Davis Medical Center, Sacramento; Dr. Jude Simon-Leack, DUR Pharmacist, EDS/Medi-Cal, Sacramento; and Dr. Loring Dales, ImmunizationBranch, Department of Health Care Services, Berkeley.