The coming flu season

Epidemics of influenza typically occur during the winter in the United States, and are responsible for an average of 36,000 deaths per year.

Epidemics of influenza typically occur during the winter in the United States, and are responsible for an average of 36,000 deaths per year. Influenza viruses also can cause pandemics during which the rates of illness and death from influenza-related complications can increase worldwide. From five to 20 percent of the American population gets the flu each year. More than 200,000 will require hospitalization. Time lost on the job and via school absenteeism annually is immense.

Influenza viruses cause disease among all age groups. Rates of infection, however, are highest among persons age 65 or older, children under age two, and people with medical conditions that place them at increased risk for influenza. Illness, complications, hospitalizations, and deaths are highest in these groups.

Influenza vaccination is the primary method for preventing influenza and its severe complications. Primary target groups recommended for annual vaccination include:

• Persons at increased risk for influenza-related complications (those age 65 or older, children ages six to 23 months, pregnant women, and people with certain chronic medical conditions);

• Persons ages 50 to 64 because they have an elevated prevalence of certain critical conditions (more than 33 percent have one or more medical conditions that place them at increased risk); and

• Persons who live with or care for those at high risk (e.g., health care workers and household contacts of high-risk people who can transmit influenza to those of high risk).

In the U.S., immunoprophylaxis requires two types of vaccine - inactivated (injected-killed virus) and live, attenuated influenza vaccine or LAIV (nasal spray). As many as 60 million people this winter could receive a “flu shot.” The inactivated vaccine can be given to anyone more than six months old. This includes healthy people, and people with chronic medical conditions. LAIV is approved for healthy people ages five to 49. Studies indicate that transmission of LAIV viruses to close contacts occurs rarely. Although price differences are decreasing, LAIV is still more expensive than killed virus injections.

Ideally, vaccination should occur in October or November. About two weeks after vaccination, antibody levels should be sufficient to afford protection. However, the flu season runs from October through May, so it is best not to delay vaccination.

Vaccine should not be given to people allergic to chicken eggs, persons who have had a previous severe reaction including Guillain-Barré syndrome, children less than six months old, and people with a fever. The latter group may be vaccinated when their symptoms resolve.

The composition of vaccine changes annually. This year, the vaccine contains three influenza viruses - two influenza A (H3N2 and H1N1) and one influenza B. The composition is based on international surveillance, and scientists’ predictions concerning the types and strains of influenza that will circulate in a given year. Such predictions have been accurate 19 of the last 20 years.

The Advisory Committee on Immunization Practices emphasizes that health care workers should be vaccinated against influenza annually. Facilities that employ health-care workers should be encouraged to provide vaccine to workers so that it maximizes immunization rates. This will help protect health care workers, patients, and the public. Dental personnel are at increased risk occupationally because of their contact daily with patient-respiratory droplets and aerosols released during treatment.

Annual vaccination among health care workers averages less than 40 percent. However, higher rates can be attained through organized campaigns. Seven states now require annual vaccination, or the signing of an informed declination. Fifteen states require vaccination of workers in long-term care facilities.

During the 2004-2005 influenza season, a shortage in vaccine supply occurred. Supplies, though, should be adequate this season. As of August, an estimated 60 to 88 million doses of killed injected vaccine will be produced by three manufacturers. An additional 10 million doses should be available after November. In addition, three million doses of LAIV are scheduled to be produced.

OSAP, the Organization for Safety & Asepsis Procedures, is dentistry’s prime source for evidence-based information on infection control and prevention, and human safety and health. More information concerning influenza transmission and prevention is available on the OSAP Web site at

Dr. Charles John Palenik is an assistant director of Infection Control Research and Services at the Indiana University School of Dentistry. Dr. Palenik is the co-author of the popular “Infection Control and Management of Hazardous Materials for the Dental Team.” He serves as chair of the OSAP publications committee. Questions about this article or any infection-control issue may be directed to

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