Influenza season is upon us. If this year is typical, 5% to 20 % of the US population will contract influenza. Of these, 200,000 people will be hospitalized and 36,000 will die. To minimize the effects of seasonal influenza, family physicians rely on annual influenza vaccine and antiviral therapy and prophylaxis. Every year at this time, we need to ask ourselves important questions as we prepare to provide maximum protection for our patients, our communities, and ourselves.
Who should receive an influenza vaccine?—an addition this year
The list of those who should receive an annual influenza vaccine (TABLE 1) is the same as last year, with 1 addition; children between ages 24 and 59 months and their household contacts and out-of-home caregivers.1-2 There are 2 types of vaccines available; trivalent inactivated influenza vaccine (TIA) and live attenuated influenza vaccine (LAIV). The TIA vaccine is administered intramuscularly, the LAIV by nasal spray. The vaccine products available and the ages for which they are licensed are listed in TABLE 2.3
The LAIV can be used for healthy people between the ages of 5 and 49 years; it should not be used for those who are pregnant, have a chronic illness, are caregivers to someone severely immune suppressed, are on chronic aspirin therapy, or have a history of Guillain-Barré syndrome. Neither vaccine should be used for anyone with an anaphylactic hypersensitivity to eggs or has had a severe allergic reaction to a previous vaccine. Vaccine should be postponed for anyone with a moderate-to-severe acute illness.
There are several other considerations for LAIV. Vaccination should be postponed for anyone with nasal congestion since it is not clear the vaccine can be administered correctly. Since LAIV is a live virus vaccine, it should be administered concurrently with, or 4 weeks after, any other live virus vaccines. It should also not be administered concurrently or within 2 weeks of receiving influenza antiviral agents. Finally, it needs to be stored at –15°C or below.
TABLE 1
Who should receive influenza vaccine
| People at high risk for complications from the flu, including: |
| Children aged 6–59 months |
| Pregnant women |
| People aged 50 years and older |
| People who live in nursing homes and other long-term care facilities |
People of any age with the following chronic medical conditions:
|
| People who live with or care for those at high risk for complications from flu, including: |
| Household contacts of persons at high risk for complications from the flu (see above) |
| Household contacts and out of home caregivers of children less than 6 months of age (these children are too young to be vaccinated) |
| Healthcare workers |
TABLE 2
Vaccine products available
| VACCINE | TRADE NAME (MANUFACTURER) | DOSE/PRESENTATION | THIMEROSAL MERCURY CONTENT (MCG/HG/0.5-ML DOSE) | AGE GROUP | NO. OF DOSES | ROUTE |
|---|---|---|---|---|---|---|
| Inactivated | ||||||
| TIV | Fluzone (Sanofi Pasteur) | 0.25-mL prefilled syringe | 0 | 6–35 mos | 1 or 2* | IM† |
| 0.5-mL prefilled syringe | 0 | ≥36 mos | 1 or 2* | IM† | ||
| 0.5-mL vial | 0 | ≥36 mos | 1 or 2* | IM† | ||
| 5.0-mL multidose vial | 25 | ≥6 mos | 1 or 2* | IM† | ||
| TIV | Fluvirin | 0.5-mL prefilled syringe | <1.0 | ≥4 years | 1 or 2* | IM† |
| 5.0-mL multidose vial | 24.5 | ≥4 years | 1 or 2* | IM† | ||
| TIV | FLUARIX (Glaxo-SmithKline) | 0.5-mL prefilled syringe | <1.25 | ≥18 years | 1 | IM† |
| Live, attenuated | ||||||
| LAIV | FluMist (Medimmune) | 0.5-mL sprayer | 0 | 5–49 years | 1 or 2‡ | Intranasal** |
| * Two doses administered at least 1 month apart are recommended for children aged 6 months to <9 years who are receiving influenza vaccine for the first time. | ||||||
| † For adults and older children, the recommended site of vaccination is the deltoid muscle. | ||||||
| The preferred site for infants and young children is the anterolateral aspect of the thigh. | ||||||
| ‡ Two doses administered at least 6 weeks apart are recommended for children aged 5 to <9 years who are receiving influenza vaccine for the first time. | ||||||
| ** One dose equals 0.5 mL, divided equally between each nostril. | ||||||
What issues are specific to ages 6 months to <9 years?
A child being immunized against influenza for the first time before his or her ninth birthday should receive 2 doses—4 weeks apart for TIV, 6 weeks apart for LAIV. The doses can be 2 of either TIV or LAIV or 1 of each. If a child received only 1 dose the prior year and it was their first time to receive the vaccine, they only need 1 dose the current year.
The supply of vaccine for this age group can be problematic, especially for age 3, for whom there is only 1 product licensed. Four of the products available for children contain trace amounts of thimerosal (TABLE 2), with the highest amounts being in multidose vials.3 There have been no proven harmful effects of these amounts of thimerosal, and both the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) continue to recommend these products. Some parents, however, may insist on a thimerosal-free product, and a few states have taken action to limit the use of thimerosal-containing vaccines.