For the 2004–2005 influenza season, the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) recommends that influenza vaccine be given to all infants and children aged 6 to 23 months.1 It further recommends vaccination for members of households that have children aged <2 years and for out-of-home caregivers for these children.
These changes will make universal coverage more difficult to achieve. Family physicians will need to educate themselves, office staff, and parents and guardians about these recommendations. Be prepared to implement office protocols that identify and notify those who require vaccination, and address the concerns of parents and guardians regarding thimerosal and the addition of yet another vaccine to the child vaccine schedule.
Rationale for change
In 2002, ACIP began to encourage use of influenza vaccine for all children 6 to 23 month old. Before then, it had been recommended only for those in that age group with certain chronic medical conditions.
Still, the coverage level achieved in the 2002 to 2003 flu season for this age group was low—only 4.4 % were fully immunized with 2 doses.2 To increase coverage, the influenza vaccine was included in vaccines offered by the Vaccine for Children program in 2003 and was made part of the universal recommendations for the coming season.
The rationale for the new universal recommendation is the high rate of influenza-related hospitalizations among those aged 6 to 23 months, which varies from year to year and has been documented to be as high as 5/1000.3,4 While hospitalization rates are higher for infants aged 0 to 5 months, influenza vaccine is not approved for use in this age group.
Death from influenza in infants and children is not common. However, in the 2003 to 2004 influenza season, 58 influenza deaths among those aged <2 years were recorded.1 Added benefits from vaccinating infants and children may include decreased rates of otitis media.5,6
Practical aspects of vaccine administration
Some of the most important practical details involved with immunizing 6- to 23-month-olds include the following:
- The age group includes those who have completed 6 months of life (are now in their 7th month) up to the second birthday. Influenza vaccine is 65% to 90% effective in this age group.
- The dose of influenza vaccine for infants and children up to their 3rd birthday is 0.25 mL.
- The vaccine should be administered intramuscularly in the anterolateral thigh with a 1-inch needle.
- Two doses, 1 month apart, are recommended for infants or children aged <9 years receiving influenza vaccine for the first time. (Dose recommendations for all age groups are listed in Table 1.)
- Only 1 vaccine product has been approved for those younger than 4 years: FluZone, produced by Aventis Pasteur.
- The vaccine is made with killed virus and can be given simultaneously with other recommended vaccines.
- The live attenuated influenza vaccine, administered intranasally, is not approved for children before their 5th birthday.
- The vaccine should be stored at 2° to 8°C (35° to 46°F) and should not be frozen.
- Vaccine left over from last year should not be used this year.
- Contraindications to influenza vaccine are listed in Table 2.
TABLE 1
Inactivated influenza vaccine* dosage, by age group
| Age group† | Dose | No of doses | Route‡ |
|---|---|---|---|
| 6–35 mo | 0.25 mL | 1 or 2§ | Intramuscular |
| 3–8 y | 0.50 mL | 1 or 2§ | Intramuscular |
| 9 y | 0.50 mL | 1 | Intramuscular |
| *A 0.5-mL dose contains 15 mg each of A/Fujian/411/2002 (H3H2)-like, A/New Caledonia/20/99 (H1N1)-like, and B/Shanghai/361/2002-like antigens. For the A/Fujian/411/2002 (H3H2)-like antigen, manufacturers may use the antigenically equivalent A/Wyoming/3/2003 (H3N2) virus, and for the B/Shanghai/361/2002-like antigen, manufacturers may use the antigenically equivalent B/Jilin/20/2003 virus or B/Jiangsu/10/2003 virus. Manufacturers include Aventis Pasteur, Inc (FluZone© split virus), and Chiron (Fluvirin™ purified surface antigen vaccine). FluZone is approved by the Food and Drug Administration for use among persons aged 6 months. Fluvirin is approved for use among persons aged 4 months. For further product information, call Aventis Pasteur at 800-822-2463 or Chiron at 800-200-4278. | |||
| † Because of their decreased potential for causing febrile reactions, only split-virus vaccines should be used for children aged <13 years. Whole-virus vaccine is not available in the United States. Split-virus vaccine might be labeled as split, subvirion, or purified surface antigen vaccine. Immunogenicity and side effects of split- and whole-virus vaccines are similar among adult when vaccines are administered in the recommended dosage. | |||
| ‡ 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 1 month apart are recommended for children aged <9 years who are receiving influenza vaccine for the first time. | |||
| Source: Harper et al 2004.1 | |||