Influenza season will, again, soon upon us. Influenza activity in the U.S. generally peaks between December and March, with vaccinations having begun in October. Flu and its complications constitute the most frequent cause of death from a vaccine-preventable disease each year.

The populations most vulnerable are the very young, those with certain chronic health conditions, anyone immune-suppressed, pregnant women and anyone 50 or older.

Healthcare providers can play important roles in preventing the spread of this highly infectious and potentially deadly disease.

Who Should Be Vaccinated?

The first line of defense against flu is vaccination. Currently, two types of influenza vaccine are available:

• Inactivated influenza vaccine (TIV) is administered as an injection by the intramuscular (IM) route. This vaccine can be administered to anyone 6 months and older.
• Live attenuated influenza vaccine (LAIV) is administered as a nasal spray. This vaccine should be administered only to non-pregnant healthy people ages 5-49 years.

The vaccines are considered equally effective. The CDC provides detailed information about TIV and LAIV in "Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP)," which is available online at www.cdc.gov/mmwr/PDF/rr/rr5408.pdf.

Children ages 6 months-8 years receiving flu vaccine for the first time require two age-appropriate doses each year. Only one dose is required annually thereafter.

Caregivers to the most vulnerable and any other household contacts, such as a maid, must also be vaccinated.

All healthcare workers should be vaccinated against influenza each year, as well. Others who should be vaccinated include all employees of assisted living, long-term care and nursing facilities. If supplies are adequate, influenza vaccination should be provided to anyone who wants to decrease his risk of contracting or transmitting the virus.

Immune protection begins approximately 2 weeks after vaccination. Peak flu vaccination activities typically occur in October and November.

However, the vaccine expiration date is not until the end of June, so providers can continue to offer flu vaccine to those who have not been vaccinated as long as the virus is still circulating and causing illness in the community. This could be late into the season (December through February and beyond.)

Clinicians As Vaccine Educators

As educators and role models, nurses should get vaccinated and encourage co-workers and patients to be vaccinated. Remind patients of the serious risks associated with flu disease and that flu vaccine does not cause disease.

Anyone administering flu vaccine should ensure the appropriate vaccine information statement (VIS) is given to each person who receives a vaccination. There is no federal requirement for signed consent, but some states or agencies may have additional requirements.

Instructions on the use of a VIS well as audio versions of VIS are available from the CDC at www.cdc.gov/nip/publications/vis. VIS is also available in more than 30 languages from the Immunization Action Coalition by visiting www.immunize.org/vis. The CDC's flu Web site (www.cdc.gov/flu) has a variety of other education materials for patients and healthcare providers as well, and is updated regularly.

Prevent Transmission

There is no substitute for vaccination, but adjunct measures can be used to decrease the spread of flu viruses. Four antiviral drugs (Symmetrel [amantadine,] Flumadine [rimantadine,] Relenza [zanamivir] and Tamiflu [oseltamivir]) are available by prescription. Each drug is approved for treatment of flu, but should be taken within 2 days of becoming sick.

With the exception of Relenza, these drugs can be used to prevent illness during outbreaks. They are about 70-90 percent effective for preventing illness in healthy adults. Specific information about the use of these agents is available at www.cdc.gov/mmwr/PDF/rr/rr5408.pdf and www.cdc.gov/flu/professionals/treatment.

CDC also offers detailed infection control guidelines online at www.cdc.gov/flu/professionals/infectioncontrol as well as information on immunization for Hurricane Katrina relief workers at www.bt.cdc.gov/disasters/hurricanes/Katrina/vaccrecdisplaced.asp.

Protect Your Vaccine Supply

Currently, only two vaccine manufacturers are licensed to supply TIV to the U.S., with another pending licensure. One manufacturer supplies LAIV. Efforts are underway to increase the number of manufacturers and develop a less-complicated method of manufacturing vaccines to avoid shortages and distribution delays witnessed in recent years. In years when supply is reduced, available vaccine must be prioritized for those at highest risk.

CDC published recommendations for "tiered" use of TIV in the event of a vaccine shortage. Detailed information on this "tiering" strategy is available at www.cdc.gov/mmwr/preview/mmwrhtml/mm5430a4.htm. Additional guidance on prioritization during the 2005-06 season is available at www.cdc.gov/mmwr/preview/mmwrhtml/mm5434a4.htm.

Along with judicious use of limited supplies, the vaccine must be stored and handled properly to avoid unnecessary wastage. However, last year's vaccine supply should not be used. Only vaccine produced for the 2005-06 influenza season should be used.

TIV should be refrigerated at 35-46º F (2-8º C) until ready to be used. LAIV should be stored in a freezer at 5º F (-15º C) or colder. It can also be stored in a refrigerator for up to 60 hours. If not used within 60 hours, LAIV cannot be refrozen and must be discarded.

Because of the lack of stability data, vaccine should not be drawn up and stored in plastic syringes hours or days before administration. Prefilling syringes can lead to vaccine contamination, reduced potency, waste and administration errors. At the end of the clinical day, if there is any vaccine remaining in syringes not filled by the manufacturer, it should be discarded.

Information on vaccine storage and handling, as well as preparing for large influenza clinics, is available in the Vaccine Storage and Handling Toolkit at www2a.cdc.gov/nip/isd/shtoolkit/splash.html.

Donna L. Weaver, MN, RN, is a nurse educator at the CDC's National Immunization Program in Atlanta.