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2007-08 INFLUENZA PREVENTION & CONTROL RECOMMENDATIONS

Influenza Vaccine Composition & Major Differences

On October 24, 2007 CDC's Advisory Committee on Immunization Practices (ACIP) recommended expanding the use of the nasal influenza vaccine LAIV (FluMist®) to include healthy children ages 2-4 years old (24-59 months old) without a history of asthma or recurrent wheezing. The vaccine continues to be recommended for healthy persons ages 5-49 years who are not pregnant. "Healthy" indicates persons who do not have an underlying medical condition that predisposes them to influenza complications.

NOTE: For 2008-09 Influenza Prevention and Control Recommendations see Prevention & Control of Influenza - Recommendations of the Advisory Committee on Immunization Practices (ACIP) 2008. MMWR 2008 Jul 17; Early Release:1-60. (Also available as PDF, 586K).

NOTE: The links below refer to text that is taken directly from  Prevention & Control of Influenza - Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 2007 Jul 13;56(RR06):1-54. Also available as PDF (720K).

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Vaccine Composition

Both LAIV and TIV contain strains of influenza viruses that are antigenically equivalent to the annually recommended strains: one influenza A (H3N2) virus, one influenza A (H1N1) virus, and one influenza B virus. Each year, one or more virus strains might be changed on the basis of global surveillance for influenza viruses and the emergence and spread of new strains. Only the H1N1 strain was changed for the recommended vaccine for the 2007–08 influenza season, compared with the 2006–07 season (see Recommendations for Using TIV and LAIV During the 2007–08 Influenza Season). Viruses for both types of currently licensed vaccines are grown in eggs. Both vaccines are administered annually to provide optimal protection against influenza virus infection (Table 3) Both TIV and LAIV are widely available in the United States. Although both types of vaccines are expected to be effective, the vaccines differ in several aspects (Table 3).

Major Differences Between TIV and LAIV

During the preparation of TIV, the vaccine viruses are made noninfectious (i.e., inactivated or killed) (91). Only subvirion and purified surface antigen preparations of TIV (often referred to as “split” and subunit vaccines, respectively) are available in the United States. TIV contains killed viruses and thus cannot cause influenza. LAIV contains live, attenuated viruses and therefore has the potential to produce mild signs or symptoms related to attenuated influenza virus infection. LAIV is administered intranasally by sprayer, whereas TIV is administered intramuscularly by injection. LAIV is currently approved only for use among healthy persons aged 5–49 years; TIV is approved for use among persons aged 6 months and older, including those who are healthy and those with chronic medical conditions (Table 3).

Table 3. Live, attenuated influenza vaccine (LAIV) compared with inactivated influenza vaccine (TIV)

Factor

 LAIV TIV
Route of administration Intranasal spray Intramuscular injection
Type of vaccine Live virus Killed virus
No. of included virus strains 3 (2 influenza A, 1 influenza B) 3 (2 influenza A, 1 influenza B)
Vaccine virus strains updated Annually Annually
Frequency of administration Annually* Annually*
Approved age and risk groups§ Healthy persons aged 5–49 yrs Persons aged 6 mos and older
Interval between 2 doses recommended for children aged >6 mos–8 years who are receiving influenza vaccine for the first time 6–10 weeks 4 weeks
Can be administered to family members or close contacts of immunosuppressed persons not requiring a protected environment Yes Yes
Can be administered to family members or close contacts of immunosuppressed persons requiring a protected environment
(e.g., hematopoietic stem cell transplant recipient)		 No Yes
Can be administered to family members or close contacts of persons at high risk but not severely immunosuppressed Yes Yes**
Can be simultaneously administered with other vaccines  Yes¶  
If not simultaneously administered, can be administered within 4 wks of another live vaccine Prudent to space 4 weeks apart  
If not simultaneously administered, can be administered within 4 wks of an inactivated vaccine Yes Yes

* Children aged 6 months and older who have never received influenza vaccine before should receive 2 doses. Those who received only 1 dose in their first year of vaccination should receive 2 doses in the following year.

† LAIV is currently licensed to be administered only to persons aged 5 years and older.

§ Annual vaccination against influenza is recommended for 1) all persons, including school-aged children, who want to reduce the risk of becoming ill with influenza or of transmitting influenza to others; 2) all children aged 6–59 months (i.e., 6 months–4 years); all persons aged 50 years and older; 3) children and adolescents (aged 6 months–18 years) receiving long-term aspirin therapy who therefore might be at risk for experiencing Reye syndrome after influenza virus infection; 4) women who will be pregnant during the influenza season; 5) adults and children who have chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, hematologic or metabolic disorders (including diabetes mellitus); 6) adults and children who have immunosuppression (including immunosuppression caused by medications or by human immunodeficiency virus ); 7) adults and children who have any condition (e.g., cognitive dysfunction, spinal cord injuries, seizure disorders, or other neuromuscular disorders) that can compromise respiratory function or the handling of respiratory secretions or that can increase the risk for aspiration; 8) residents of nursing homes and other chronic-care facilities; 9) healthcare workers; 10) healthy household contacts (including children) and caregivers of children aged <5 years and adults aged >50 years, with particular focus on vaccinating contacts of children aged <6 months; and 11) healthy household contacts (including children) and caregivers of persons with medical conditions that put them at higher risk for severe complications from influenza. However, no vaccine is approved for children aged <6 months.

¶ No data are available regarding effect on safety or efficacy.

** Inactivated influenza vaccine coadministration has been evaluated systematically only among adults with pneumococcal polysaccharide vaccine.

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